New Data on the Early Triassic Land Flora Recovery
Yu, J., Broutin, J., Huang, Q., and L. Grauvogel-Stamm. 2010. Annalepis, a pioneering lycopsid genus in the recovery of the Triassic land flora in South China. Comptes Rendus Palevol 9:479-486. doi:10.1016/j.crpv.2010.09.004 Abstract - Fossil plants are scarce in the Earliest Triassic marine deposits of western Guizhou and eastern Yunnan. Only Annularia shirakii, Lobatannularia sp., Paracalamites stenocostatus, Gigantopteris sp., Pecopteris sp. were reported from the base of the Kayitou Formation dated as Early Induan by marine fauna. Recently, we discovered numerous representatives of the genus Annalepis in the same Lowermost Triassic beds: A. latiloba, A. brevicystis, A. angusta, Annalepis spp. occur associated with a basal Triassic marine fauna. This discovery fills the biostratigraphic gap between the Late Permian “Gigantonoclea guizhouensis-Ullmannia cf. bronnii-Annularia pingloensis” and the late Lower Triassic “Neuropteridium–Albertia–Voltzia” assemblages reported from South China. It represents an important datum dealing with the very beginning of a new terrestrial flora installation after the Permian flora disappearance following the Permian–Triassic boundary mass extinction. This “starting point” of a new vegetal cover in South China is to be taken into account in reconstructing through space and time the settlement process of the Mesozoic floristic provinces.
Pterosaurs are Archosauriforms
Nesbitt, S. J., and D. W. E. Hone. 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233.
Abstract - Pterosauria, a successful clade of extinct flying vertebrates, possesses a radical body plan that offers few clues about their origin and closest relatives. Whereas most researchers hypothesize an origin within Archosauria as the sister-group to Dinosauromorpha, others favor a position among non archosauriform archosauromorphs. Here we present evidence that supports a placement within Archosauriformes: the presence of an external mandibular fenestra in two basal pterosaur taxa, Dimorphodon macronyx and a specimen referred to Eudimorphodon cf. ranzii (= ‘Seefeld Eudimorphodon’; BSP 1994 I 51). Furthermore, the arrangement of the mandibular bones surrounding the mandibular fenestra and the presence of a posterior process of the dentary that laterally overlaps the angular in the mandible of Dimorphodon and BSP 1994 I 51 are identical to those of Erythrosuchus, Euparkeria, and Archosauria. When mapped on a cladogram, presence or absence of an external mandibular fenestra in basal pterosaurs possibly indicates that the feature is primitive for Pterosauria but later lost. The presence of an external mandibular fenestra, along with morphological evidence elsewhere in the body of pterosaurs(serrated teeth, antorbital fossa present, fourth trochanter on the femur present), supports a placement of Pterosauria within Archosauriformes and is consistent with a position within Archosauria.
Abstract - Pterosauria, a successful clade of extinct flying vertebrates, possesses a radical body plan that offers few clues about their origin and closest relatives. Whereas most researchers hypothesize an origin within Archosauria as the sister-group to Dinosauromorpha, others favor a position among non archosauriform archosauromorphs. Here we present evidence that supports a placement within Archosauriformes: the presence of an external mandibular fenestra in two basal pterosaur taxa, Dimorphodon macronyx and a specimen referred to Eudimorphodon cf. ranzii (= ‘Seefeld Eudimorphodon’; BSP 1994 I 51). Furthermore, the arrangement of the mandibular bones surrounding the mandibular fenestra and the presence of a posterior process of the dentary that laterally overlaps the angular in the mandible of Dimorphodon and BSP 1994 I 51 are identical to those of Erythrosuchus, Euparkeria, and Archosauria. When mapped on a cladogram, presence or absence of an external mandibular fenestra in basal pterosaurs possibly indicates that the feature is primitive for Pterosauria but later lost. The presence of an external mandibular fenestra, along with morphological evidence elsewhere in the body of pterosaurs(serrated teeth, antorbital fossa present, fourth trochanter on the femur present), supports a placement of Pterosauria within Archosauriformes and is consistent with a position within Archosauria.
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| from Nesbitt & Hone 2010 - Palaeodiversitas 3 |
An Upclose Look at the Microanatomy of Aetosaur Osteoderms
Aetosaurs are characterized by their elaborate bony carapaces composed of numerous osteoderms. In fact aetosaur taxonomy is almost based solely on the morphology (especially the surface ornamentation) of osteoderms. Despite this detailed studies of the microstructure of aetosaur oseoderms are lacking. In 2008 I published a paper with Michelle Stocker and Randall Irmis that provided the first histological data for aetosaur osteoderms, but we were mostly looking at providing an estimated age at time of death for the holotype of Sierritasuchus macalpini to determine the ontogenetic stage of the specimen.
This new study focuses on aetosaurine osteoderms from Argentina and Brazil, including specimens assigned to Aetosauroides scagliai. One of the very cool things these authors did was not only to look a parasaggital sections of the rectangular osteoderms, they also looked at transverse sections. Some of the key findings are as follows:
- Aetosaur osteoderms lend themselves well to this type of study as secondary remodeling is minimal.
-Unlike all other sampled archosaurs, aetosaur osteoderm ossification was not metaplastic in nature (i.e. pre-existing, fully developed tissue is ossified), instead the osteoderms seemingly underwent intermembraneous ossification where new tissue displaces preformed tissue rather than incorporating it. This is currently unique among archosaurs.
- Cyclic growth lines (Lines of arrested growth of LAG's) are well developed. Based on this the specimens sampled belonged to a range of subadult animals between two and nine years of age at time of death (minimum ages).
- The center of ossification in aetosaur osteoderms is at the level of the raised dorsal eminence.
- Aetosaur plates probably grew by adding peripheral layers. Interestingly most faster growth occurred along the medial and lateral margins. This accounts for the assymetrical placement of the dorsal eminence that is characteristic of aetosaurines.
- Well-developed Sharpey's fibers along the medial and lateral margins of the osteoderms suggest strong lateral and medial attachments along a row of osteoderms. In contrast the attachments with anterior of posterior plates were poor, presumably allowing for flexion and movement in the carapace.
-Finally, the ornamentation of the osteoderms is formed by local resorption and partitial redeposition of the cortical bone. Acceleration of growth in particular areas enhances the degree of sculpture through time and the pattern is established early and then maintained through future growth. This is seemingly why the ornamentation in juvenile specimens does not differ significantly from that of adults. This is extremely significant if you are using this patterning to diagnose taxa.
Overall an important study and excellent paper.
Cerda, I. A., and J. B. Desojo. 2010: Dermal armour histology of aetosaurs (Archosauria: Pseudosuchia), from the Upper Triassic of Argentina and Brazil. Lethaia, DOI: 10.1111/j.1502-3931.2010.00252.x.
Abstract - One of the most striking features documented in aetosaurs is the presence of an extensive bony armour composed of several osteoderms. Here, we analyse the bone microstructure of these elements in some South American Aetosaurinae aetosaurs, including Aetosauroides scagliai. In general terms, Aetosaurinae osteoderms are compact structures characterized by the presence of three tissue types: a basal cortex of poorly vascularized parallel-fibred bone tissue, a core of highly vascularized fibro-lamellar bone, and an external cortex of rather avascular lamellar bone tissue. Sharpey’s fibres are more visible at the internal core, toward the lateral margins and aligned parallel to the major axis of the dermal plate. No evidence of metaplastic origin is reported in the osteoderms, and we hypothesize an intramembranous ossification for these elements. The bone tissue distribution reveals that the development of the osteoderm in Aetosaurinae starts in a position located medial to the plate midpoint, and the main sites of active osteogenesis occur towards the lateral and medial edges of the plate. The osteoderm ornamentation is originated and maintained by a process of resorption and redeposition of the external cortex, which also includes preferential bone deposition in some particular sites. Given that no secondary reconstruction occurs in the osteoderms, growth marks are well preserved and they provide very important information regarding the relative age and growth pattern of Aetosaurinae aetosaurs.
This new study focuses on aetosaurine osteoderms from Argentina and Brazil, including specimens assigned to Aetosauroides scagliai. One of the very cool things these authors did was not only to look a parasaggital sections of the rectangular osteoderms, they also looked at transverse sections. Some of the key findings are as follows:
- Aetosaur osteoderms lend themselves well to this type of study as secondary remodeling is minimal.
-Unlike all other sampled archosaurs, aetosaur osteoderm ossification was not metaplastic in nature (i.e. pre-existing, fully developed tissue is ossified), instead the osteoderms seemingly underwent intermembraneous ossification where new tissue displaces preformed tissue rather than incorporating it. This is currently unique among archosaurs.
- Cyclic growth lines (Lines of arrested growth of LAG's) are well developed. Based on this the specimens sampled belonged to a range of subadult animals between two and nine years of age at time of death (minimum ages).
- The center of ossification in aetosaur osteoderms is at the level of the raised dorsal eminence.
- Aetosaur plates probably grew by adding peripheral layers. Interestingly most faster growth occurred along the medial and lateral margins. This accounts for the assymetrical placement of the dorsal eminence that is characteristic of aetosaurines.
- Well-developed Sharpey's fibers along the medial and lateral margins of the osteoderms suggest strong lateral and medial attachments along a row of osteoderms. In contrast the attachments with anterior of posterior plates were poor, presumably allowing for flexion and movement in the carapace.
-Finally, the ornamentation of the osteoderms is formed by local resorption and partitial redeposition of the cortical bone. Acceleration of growth in particular areas enhances the degree of sculpture through time and the pattern is established early and then maintained through future growth. This is seemingly why the ornamentation in juvenile specimens does not differ significantly from that of adults. This is extremely significant if you are using this patterning to diagnose taxa.
Overall an important study and excellent paper.
Cerda, I. A., and J. B. Desojo. 2010: Dermal armour histology of aetosaurs (Archosauria: Pseudosuchia), from the Upper Triassic of Argentina and Brazil. Lethaia, DOI: 10.1111/j.1502-3931.2010.00252.x.
Abstract - One of the most striking features documented in aetosaurs is the presence of an extensive bony armour composed of several osteoderms. Here, we analyse the bone microstructure of these elements in some South American Aetosaurinae aetosaurs, including Aetosauroides scagliai. In general terms, Aetosaurinae osteoderms are compact structures characterized by the presence of three tissue types: a basal cortex of poorly vascularized parallel-fibred bone tissue, a core of highly vascularized fibro-lamellar bone, and an external cortex of rather avascular lamellar bone tissue. Sharpey’s fibres are more visible at the internal core, toward the lateral margins and aligned parallel to the major axis of the dermal plate. No evidence of metaplastic origin is reported in the osteoderms, and we hypothesize an intramembranous ossification for these elements. The bone tissue distribution reveals that the development of the osteoderm in Aetosaurinae starts in a position located medial to the plate midpoint, and the main sites of active osteogenesis occur towards the lateral and medial edges of the plate. The osteoderm ornamentation is originated and maintained by a process of resorption and redeposition of the external cortex, which also includes preferential bone deposition in some particular sites. Given that no secondary reconstruction occurs in the osteoderms, growth marks are well preserved and they provide very important information regarding the relative age and growth pattern of Aetosaurinae aetosaurs.
Pangean Great Lake Paleoecology on the Cusp of the End-Triassic Extinction
Very cool study of the fish community in a large scale lake responding to changing environmental conditions during the earliest Jurassic.
Whiteside, J. H., Olsen, P. E., Eglinton, T. I., Cornet, B., McDonald, N. G., and P. Huber. In press. Pangean great lake paleoecology on the cusp of the end-Triassic extinction. Palaeogeography (2010), doi:10.1016/j.palaeo.2010.11.025.
Abstract - Triassic and Early Jurassic age lacustrine deposits of eastern North American rift basins preserve a spectacular record of precession-related Milankovitch forcing in the Pangean tropics in the wake of the end-Triassic extinction event (ETE). The abundant and well preserved fossil fish assemblages from these great lakes show cyclical changes that track the permeating hierarchy of climatic cycles. To detail ecosystem processes correlating with succession of fish communities, bulk δ13C was measured through a 100 ky series of precession-forced lake level cycles in the lower Shuttle Meadow Formation of the Hartford rift basin, Connecticut that were deposited within 50 ky after the ETE. The deep-water phase of one of these cycles, the Bluff Head Bed, has produced thousands of articulated fish. There are fluctuations in the bulk δ13Corg in the cyclical strata that reflect differing degrees of lake water stratification, nutrient levels, and relative proportion of algal vs. plant derived organic matter that trace fish community changes. Extrinsic changes in the global exchangeable reservoirs can be excluded as an origin of this variability because molecule-level δ13C of n-alkanes from plant leaf waxes in the same strata show no such variability. Although higher taxonomic levels of the fish communities responded largely by sorting of taxa by environmental forcing, at the species level the holostean genus Semionotus responded by in situ evolution, and ultimately extinction, of a species flock. Fluctuations at the higher frequency, climatic precessional scale are mirrored at lower frequency, eccentricity modulated, scales, all following the lake-level hierarchical pattern. Thus, changes in lacustrine isotopic ratios amplify the Milankovitch climate signal that was already intensified by sequelae of the end-Triassic extinctions. The degree to which the ecological structure of modern lakes responds to similar environmental cyclicity is largely unknown, but similar patterns and processes are present within the Neogene history of the East African great lakes.
Whiteside, J. H., Olsen, P. E., Eglinton, T. I., Cornet, B., McDonald, N. G., and P. Huber. In press. Pangean great lake paleoecology on the cusp of the end-Triassic extinction. Palaeogeography (2010), doi:10.1016/j.palaeo.2010.11.025.
Abstract - Triassic and Early Jurassic age lacustrine deposits of eastern North American rift basins preserve a spectacular record of precession-related Milankovitch forcing in the Pangean tropics in the wake of the end-Triassic extinction event (ETE). The abundant and well preserved fossil fish assemblages from these great lakes show cyclical changes that track the permeating hierarchy of climatic cycles. To detail ecosystem processes correlating with succession of fish communities, bulk δ13C was measured through a 100 ky series of precession-forced lake level cycles in the lower Shuttle Meadow Formation of the Hartford rift basin, Connecticut that were deposited within 50 ky after the ETE. The deep-water phase of one of these cycles, the Bluff Head Bed, has produced thousands of articulated fish. There are fluctuations in the bulk δ13Corg in the cyclical strata that reflect differing degrees of lake water stratification, nutrient levels, and relative proportion of algal vs. plant derived organic matter that trace fish community changes. Extrinsic changes in the global exchangeable reservoirs can be excluded as an origin of this variability because molecule-level δ13C of n-alkanes from plant leaf waxes in the same strata show no such variability. Although higher taxonomic levels of the fish communities responded largely by sorting of taxa by environmental forcing, at the species level the holostean genus Semionotus responded by in situ evolution, and ultimately extinction, of a species flock. Fluctuations at the higher frequency, climatic precessional scale are mirrored at lower frequency, eccentricity modulated, scales, all following the lake-level hierarchical pattern. Thus, changes in lacustrine isotopic ratios amplify the Milankovitch climate signal that was already intensified by sequelae of the end-Triassic extinctions. The degree to which the ecological structure of modern lakes responds to similar environmental cyclicity is largely unknown, but similar patterns and processes are present within the Neogene history of the East African great lakes.
Surprise! Scientists now say that Crocodiles are not "Living Fossils".
Here are some excerpts from a BBC article that was posted online today:
"Crocodiles can no longer be referred to as "living fossils", according to scientists".
"Members of the crocodilian [sic] family have previously been thought to have changed little since prehistoric times. However, new fossil analyses suggests that modern crocodilians actually evolved from a very diverse group".
"Recently discovered ancient ancestors include small cat-like specimens, giant "supercrocs" and a pug-nosed vegetarian species".
"Modern crocodilians are adapted to aquatic environments with long snouts, strong tails and powerful jaws. Yet contrary to popular belief, scientists now suggest that the basic body structure of crocodiles, alligators and ghariels [sic] evolved from a diverse group of prehistoric reptiles with different body shapes".
You can read the rest of this story here. I am always flabbergasted how these "popular beliefs" still persist and how this "revelation" can be considered new.
Can't wait to get my copy of the new JVP memoir though. It sounds incredible.
"Crocodiles can no longer be referred to as "living fossils", according to scientists".
"Members of the crocodilian [sic] family have previously been thought to have changed little since prehistoric times. However, new fossil analyses suggests that modern crocodilians actually evolved from a very diverse group".
"Recently discovered ancient ancestors include small cat-like specimens, giant "supercrocs" and a pug-nosed vegetarian species".
"Modern crocodilians are adapted to aquatic environments with long snouts, strong tails and powerful jaws. Yet contrary to popular belief, scientists now suggest that the basic body structure of crocodiles, alligators and ghariels [sic] evolved from a diverse group of prehistoric reptiles with different body shapes".
You can read the rest of this story here. I am always flabbergasted how these "popular beliefs" still persist and how this "revelation" can be considered new.
Can't wait to get my copy of the new JVP memoir though. It sounds incredible.
Two New Cynodont Papers from the Middle Triassic of Gondwana
The first paper is a short note so there is no abstract.
Kammerer, C. F., Flynn, J. J., Ranivoharimanana, L. and A. R. Wyss. 2010. The first record of a probainognathian (Cynodontia: Chiniquodontidae) from the Triassic of Madagascar. Journal of Vertebrate Paleontology 30:1889-1894. DOI: 10.1080/02724634.2010.520784
Note: The authors state that this specimen is probably Middle Triassic in age, but could possibly be as young as Carnian.
Martinelli, A. G. 2010. On the postcanine dentition of Pascualgnathus polanskii Bonaparte (Cynodontia, Traversodontidae) from the Middle Triassic of Argentina. Geobios 43:629–638
Abstract - The dental morphology of Pascualgnathus polanskii Bonaparte (Therapsida, Eucynodontia, Traversodontidae), from the Middle Triassic RÃo Seco de la Quebrada Formation (Puesto Viejo Group, Argentina), is described and compared with that of other basal traversodontid cynodonts. Albeit Pascualgnathus is frequently used in phylogenetic analyses, neither a detailed description nor drawings of its postcanines have been published so far. The upper postcanines of Pascualgnathus are transversely wide, rectangular in occlusal view, with a lingual cusp connected to the transverse ridge which is located in the center of the crown, and one main labial cusp followed by one posterior labial, both forming the labial margin. The lower postcanines, mostly worn out in the known specimens, are quadrangular until pc6 and then they are rectangular with the major axis anteroposteriorly oriented. They have a tall mesial border, possibly constituted by one labial and one lingual cusp, and a transverse ridge. After comparisons, the number of cusps in the sectorial, labial border of the upper gomphodont teeth, frequently used in phylogenetic analyses, would not necessary implies real homologies. For example, postcanine morphologies with one or more cusps anterior to the main labial cusp would not be homologous to morphologies with one or more cusps posterior to the main labial cusp, while resulting in a similar count of labial cusps.
Kammerer, C. F., Flynn, J. J., Ranivoharimanana, L. and A. R. Wyss. 2010. The first record of a probainognathian (Cynodontia: Chiniquodontidae) from the Triassic of Madagascar. Journal of Vertebrate Paleontology 30:1889-1894. DOI: 10.1080/02724634.2010.520784
Note: The authors state that this specimen is probably Middle Triassic in age, but could possibly be as young as Carnian.
Martinelli, A. G. 2010. On the postcanine dentition of Pascualgnathus polanskii Bonaparte (Cynodontia, Traversodontidae) from the Middle Triassic of Argentina. Geobios 43:629–638
Abstract - The dental morphology of Pascualgnathus polanskii Bonaparte (Therapsida, Eucynodontia, Traversodontidae), from the Middle Triassic RÃo Seco de la Quebrada Formation (Puesto Viejo Group, Argentina), is described and compared with that of other basal traversodontid cynodonts. Albeit Pascualgnathus is frequently used in phylogenetic analyses, neither a detailed description nor drawings of its postcanines have been published so far. The upper postcanines of Pascualgnathus are transversely wide, rectangular in occlusal view, with a lingual cusp connected to the transverse ridge which is located in the center of the crown, and one main labial cusp followed by one posterior labial, both forming the labial margin. The lower postcanines, mostly worn out in the known specimens, are quadrangular until pc6 and then they are rectangular with the major axis anteroposteriorly oriented. They have a tall mesial border, possibly constituted by one labial and one lingual cusp, and a transverse ridge. After comparisons, the number of cusps in the sectorial, labial border of the upper gomphodont teeth, frequently used in phylogenetic analyses, would not necessary implies real homologies. For example, postcanine morphologies with one or more cusps anterior to the main labial cusp would not be homologous to morphologies with one or more cusps posterior to the main labial cusp, while resulting in a similar count of labial cusps.
Lamy Amphibian Quarry Taphonomy Redux and "Forensic Taphonomy"
The Lamy amphibian quarry is a famous quarry in the Garita Creek (=Tecovas) Formation of the Dockum Group in New Mexico. The quarry is well known for its large assemblage of metoposaurs, all presumably belonging to the taxon Koskinonodon perfectum (previously known as Buettneria perfecta). Anyone who has visited the Triassic portion of the Smithsonian Museum of Natural History in Washington, D.C. has probably seen the block of metoposaur skulls from this quarry on exhibit. It was originally interpreted to represent a group of metoposaurs dying in a small body of water dessicated by drought, but this new study proposes little evidence of this. Furthermore, the quarry was reopened and new blocks collected providing new information.
This paper also coins a new term "forensic taphonomy", which is the study of the taphonomy of a site solely utilizing field notes and previous publications without actually visiting the study area first hand. This type of work had been done previously for this site and while these authors defend this type of study in general, I'm left with the overall feeling that it is bad practice to discuss something as dependent on the proper interpretation of sedimentary structures and specimen orientations as taphomony without first hand observation of the site. Therefore, I'm glad they have revised their previous work by actually getting access to and reopening the quarry.
Finally, the authors briefly discuss an important caveat when studying specimens collected from bone-beds decades ago. To highlight what was thought to be key elements of the quarry, in this case the metoposaur skulls, the exhibitors had staff cover over many of the smaller bones around the skulls such as limb bones. Thus "forensic taphonomy" interpretations based on this display block were skewed by the preparation and exhibit technique used. This type of technique was also used to highlight two Coelophysis skeletons from the Late Triassic Coelophysis quarry, which are on exhibit at the American Museum of Natural History. "Undesirable" bones were removed or covered over, and tails were added to these specimens to make them complete. Recent preparation techniques discourage the use of materials to mimic bone to make specimens appear complete, and also the past practice of amalgamating different specimens in bone panel mounts such as these. Indeed, it can be extremely difficult to study older specimens prepared in this manner, as features of the specimens may not be real. In fact some older, well known specimen descriptions actually describe the reconstruction, not the real bones. Be careful out there.
Lucas, S. G., Rinehart, L. F., Krainer, K., Spielmann, J. A., and A. B. Heckert. 2010. Taphonomy of the Lamy amphibian quarry: A Late Triassic bonebed in New Mexico, U.S.A. Palaeogeography, Palaeoclimatology, Palaeoecology 298:388–398. doi:10.1016/j.palaeo.2010.10.025
Abstract - Located in Santa Fe County, New Mexico, USA, the Lamy amphibian quarry is a Late Triassic (Adamanian) bonebed stratigraphically low in the Garita Creek Formation of the Chinle Group. Well known for its mass accumulation of metoposaurid amphibians, it was initially interpreted as a drought-induced death assemblage. Based on microstratigraphic and sedimentological studies, additional and extensive collecting at the quarry and a revised understanding of the bonebed, we provide a detailed taphonomic analysis of the Lamy amphibian quarry that identifies it as a low diversity multitaxic and monodominant bonebed in pedogenically modified floodplain mudstone. The Lamy bonebed shows no evidence of drought and is characterized by a high density of completely dissociated bones that show clear alignment by current and sorting (enrichment of Voorhies Group II and III elements). The bones show no significant abrasion or weathering (stage 0), preserve virtually no evidence of scavenging and show no evidence of trampling. Based on skull lengths, the metoposaurid assemblage has a type I survivorship curve and lacks juveniles. We thus posit that the following sequence of events formed the Lamy amphibian bonebed: (1) aggregation (cause unknown) of a large number of metoposaurid amphibians at a site different from the location of the bonebed, though not distant; (2) catastrophic mass mortality; (3) complete disarticulation and disassociation of the skeletons; and (4) rapid transport of the disarticulated bones onto a floodplain surface that was undergoing pedogenesis. The Lamy amphibian bonebed is representative of the Late Triassic metoposaurid bonebeds from Morocco and the western USA, which are monodominant and nearly monotaxic. They indicate that aggregation (probably of breeding populations) and mass death of metoposaurids were relatively common across the riverine floodplains of Late Triassic Pangea.
This paper also coins a new term "forensic taphonomy", which is the study of the taphonomy of a site solely utilizing field notes and previous publications without actually visiting the study area first hand. This type of work had been done previously for this site and while these authors defend this type of study in general, I'm left with the overall feeling that it is bad practice to discuss something as dependent on the proper interpretation of sedimentary structures and specimen orientations as taphomony without first hand observation of the site. Therefore, I'm glad they have revised their previous work by actually getting access to and reopening the quarry.
Finally, the authors briefly discuss an important caveat when studying specimens collected from bone-beds decades ago. To highlight what was thought to be key elements of the quarry, in this case the metoposaur skulls, the exhibitors had staff cover over many of the smaller bones around the skulls such as limb bones. Thus "forensic taphonomy" interpretations based on this display block were skewed by the preparation and exhibit technique used. This type of technique was also used to highlight two Coelophysis skeletons from the Late Triassic Coelophysis quarry, which are on exhibit at the American Museum of Natural History. "Undesirable" bones were removed or covered over, and tails were added to these specimens to make them complete. Recent preparation techniques discourage the use of materials to mimic bone to make specimens appear complete, and also the past practice of amalgamating different specimens in bone panel mounts such as these. Indeed, it can be extremely difficult to study older specimens prepared in this manner, as features of the specimens may not be real. In fact some older, well known specimen descriptions actually describe the reconstruction, not the real bones. Be careful out there.
Lucas, S. G., Rinehart, L. F., Krainer, K., Spielmann, J. A., and A. B. Heckert. 2010. Taphonomy of the Lamy amphibian quarry: A Late Triassic bonebed in New Mexico, U.S.A. Palaeogeography, Palaeoclimatology, Palaeoecology 298:388–398. doi:10.1016/j.palaeo.2010.10.025
Abstract - Located in Santa Fe County, New Mexico, USA, the Lamy amphibian quarry is a Late Triassic (Adamanian) bonebed stratigraphically low in the Garita Creek Formation of the Chinle Group. Well known for its mass accumulation of metoposaurid amphibians, it was initially interpreted as a drought-induced death assemblage. Based on microstratigraphic and sedimentological studies, additional and extensive collecting at the quarry and a revised understanding of the bonebed, we provide a detailed taphonomic analysis of the Lamy amphibian quarry that identifies it as a low diversity multitaxic and monodominant bonebed in pedogenically modified floodplain mudstone. The Lamy bonebed shows no evidence of drought and is characterized by a high density of completely dissociated bones that show clear alignment by current and sorting (enrichment of Voorhies Group II and III elements). The bones show no significant abrasion or weathering (stage 0), preserve virtually no evidence of scavenging and show no evidence of trampling. Based on skull lengths, the metoposaurid assemblage has a type I survivorship curve and lacks juveniles. We thus posit that the following sequence of events formed the Lamy amphibian bonebed: (1) aggregation (cause unknown) of a large number of metoposaurid amphibians at a site different from the location of the bonebed, though not distant; (2) catastrophic mass mortality; (3) complete disarticulation and disassociation of the skeletons; and (4) rapid transport of the disarticulated bones onto a floodplain surface that was undergoing pedogenesis. The Lamy amphibian bonebed is representative of the Late Triassic metoposaurid bonebeds from Morocco and the western USA, which are monodominant and nearly monotaxic. They indicate that aggregation (probably of breeding populations) and mass death of metoposaurids were relatively common across the riverine floodplains of Late Triassic Pangea.
Preserved Bark on Middle Triassic Gymnosperm Wood from Antarctica
Bark is rarely preserved in fossil trees so this is pretty significant.
Decombeix, A.-L., Taylor, E. L., and T. N. Taylor. 2010. Anatomy and affinities of permineralized gymnospermous trunks with preserved bark from the Middle Triassic of Antarctica. Review of Palaeobotany and Palynology 163:26–34. doi:10.1016/j.revpalbo.2010.09.002
Abstract - Permineralized gymnosperm axes with pycnoxylic wood from the Middle Triassic Fremouw Formation of the Central Transantarctic Mountains, Antarctica, are assigned to the corystosperms (seed ferns) and conifers. Both groups have been previously described from this formation based on juvenile stems with attached leaf bases and decorticated trunks. Here we describe large axes with preserved bark from the Fremouw Peak permineralized peat locality. The specimens are characterized by a small parenchymatous pith with clusters of sclereids, a thick cylinder (> 10 cm) of pycnoxylic wood, and 1–2 cm of bark containing distinctive clusters of sclereids and a complex system of cortical vascular bundles. Comparison with axes previously described from the Middle Triassic of Antarctica shows that the new specimens are most similar to Kykloxylon, a corystosperm genus based on young stems bearing Dicroidium leaves, and with a portion of axis previously described as Rhexoxylon like. We suggest that both the new specimens and the Rhexoxylon-like axis represent proximal parts of a Dicroidium/Kykloxylon plant that possibly had a fluted trunk base, and we discuss the problem of delimiting features in corystosperm axes.
Decombeix, A.-L., Taylor, E. L., and T. N. Taylor. 2010. Anatomy and affinities of permineralized gymnospermous trunks with preserved bark from the Middle Triassic of Antarctica. Review of Palaeobotany and Palynology 163:26–34. doi:10.1016/j.revpalbo.2010.09.002
Abstract - Permineralized gymnosperm axes with pycnoxylic wood from the Middle Triassic Fremouw Formation of the Central Transantarctic Mountains, Antarctica, are assigned to the corystosperms (seed ferns) and conifers. Both groups have been previously described from this formation based on juvenile stems with attached leaf bases and decorticated trunks. Here we describe large axes with preserved bark from the Fremouw Peak permineralized peat locality. The specimens are characterized by a small parenchymatous pith with clusters of sclereids, a thick cylinder (> 10 cm) of pycnoxylic wood, and 1–2 cm of bark containing distinctive clusters of sclereids and a complex system of cortical vascular bundles. Comparison with axes previously described from the Middle Triassic of Antarctica shows that the new specimens are most similar to Kykloxylon, a corystosperm genus based on young stems bearing Dicroidium leaves, and with a portion of axis previously described as Rhexoxylon like. We suggest that both the new specimens and the Rhexoxylon-like axis represent proximal parts of a Dicroidium/Kykloxylon plant that possibly had a fluted trunk base, and we discuss the problem of delimiting features in corystosperm axes.
Embryonic Skeletal Morphology of the Jurassic Sauropodomorph Massospondylus
A few weeks ago I mentioned an upcoming article on sauropodomorph embryos from the Lower Jurassic of South Africa. That article is now published in the Journal of Vertebrate Paleontology. This find represents the oldest occurrence of dinosaur embryonic material, but it also represents one of the oldest records of eggshell in the fossil record. As far as I am aware (and someone please correct me if I am wrong) the only occurence of fossil eggs in the Triassic were associated with hatchlings of the sauropodomorph Mussaurus from the Upper Triassic El Tranquilo Formation of Argentina (Bonaparte and Vince, 1979). No calcified eggs are known from the Permian or earlier (Hirsch, 1979). Having worked in Cretaceous units where fossil eggshell is ubiquitous I'm always been curious about the lack of fossil eggshell in the Triassic. Years back I suggested that maybe fully calcified eggs hadn't developed yet, but was told by someone purportedly knowledgeable in fossil eggs that they were present, I just didn't know what look for. I'm not really advocating my initial suggestion, but I'm not buying the latter explanation either. Anyone else have any thoughts?
Reisz, R. R. , Evans, D. C. , Sues, H.-D. and D. Scott. 2010. Embryonic skeletal anatomy of the sauropodomorph dinosaur Massospondylus from the Lower Jurassic of South Africa. Journal of Vertebrate Paleontology 30:1653-1665. DOI:10.1080/02724634.2010.521604
Abstract - Two embryonic skeletons preserved inside thin-shelled eggs of a partially preserved clutch from the Upper Elliot Formation (Lower Jurassic) of South Africa have been attributed to the sauropodomorph dinosaur Massospondylus carinatus. A virtually complete skeleton is exposed in right lateral view, with the slightly telescoped skull and several cervical vertebrae extending beyond the eggshell. A second, partial skeleton has a skull preserved in dorsal view. The embryos have proportionately very large skulls, with the broad skull table formed by wide parietals and frontals. The wide posterolateral wing of the frontal separates the postorbital from contact with the parietal. The embryos have short rather than elongated cervical vertebrae, with tall rather than low neural arches. The large forelimbs are only slightly shorter than the hind limbs, which suggests an obligatory quadrupedal posture for the hatchlings. This pattern may represent an ontogenetic constraint related to the large size of the head and horizontally oriented neck. Similarities between the embryonic and post-hatchling specimens include the slenderness of the lower jaw and slight ventral curvature of the symphyseal portion of the dentary, the large supraorbital process of the prefrontal, and the tall antorbital and infratemporal fenestrae. There are 10 cervical, 14 dorsal, and three sacral vertebrae. The large distal claw-bearing phalanx of manual digit 1 is longer than any other phalangeal element of either manus or pes. The embryos of Massospondylus carinatus represent the oldest dinosaurian embryos known to date.
Reisz, R. R. , Evans, D. C. , Sues, H.-D. and D. Scott. 2010. Embryonic skeletal anatomy of the sauropodomorph dinosaur Massospondylus from the Lower Jurassic of South Africa. Journal of Vertebrate Paleontology 30:1653-1665. DOI:10.1080/02724634.2010.521604
Abstract - Two embryonic skeletons preserved inside thin-shelled eggs of a partially preserved clutch from the Upper Elliot Formation (Lower Jurassic) of South Africa have been attributed to the sauropodomorph dinosaur Massospondylus carinatus. A virtually complete skeleton is exposed in right lateral view, with the slightly telescoped skull and several cervical vertebrae extending beyond the eggshell. A second, partial skeleton has a skull preserved in dorsal view. The embryos have proportionately very large skulls, with the broad skull table formed by wide parietals and frontals. The wide posterolateral wing of the frontal separates the postorbital from contact with the parietal. The embryos have short rather than elongated cervical vertebrae, with tall rather than low neural arches. The large forelimbs are only slightly shorter than the hind limbs, which suggests an obligatory quadrupedal posture for the hatchlings. This pattern may represent an ontogenetic constraint related to the large size of the head and horizontally oriented neck. Similarities between the embryonic and post-hatchling specimens include the slenderness of the lower jaw and slight ventral curvature of the symphyseal portion of the dentary, the large supraorbital process of the prefrontal, and the tall antorbital and infratemporal fenestrae. There are 10 cervical, 14 dorsal, and three sacral vertebrae. The large distal claw-bearing phalanx of manual digit 1 is longer than any other phalangeal element of either manus or pes. The embryos of Massospondylus carinatus represent the oldest dinosaurian embryos known to date.
Unique Carapace Structure in a Triassic Tetrapod
Wow, and I thought that aetosaur carapaces were complex. Osteoderms provide more than defense and display. They also provide support and stabilization for the axial skeleton. Choniosuchians seem to take this to a unique level.
Buchwitz, M. and S. Voigt. 2010. Peculiar carapace structure of a Triassic chroniosuchian implies evolutionary shift in trunk flexibility. Journal of Vertebrate Paleontology 30:1697-1708. DOI: 10.1080/02724634.2010.521685
Abstract - Dermal ossifications are widespread in Permian and Triassic tetrapods, but only members of the Chroniosuchia possess a series of dorsal osteoderms with a complex plate-to-plate articulation mechanism in addition to a contact between each osteoderm and its associated vertebral spine. The stratigraphically youngest chroniosuchid, Madygenerpeton pustulatus, from the Triassic of Kyrgyzstan provides new insight on the function of the chroniosuchian osteoderm system. Osteoderms of M. pustulatus are broad, peaked-roof-shaped to arched, with enlarged posterodorsal and anteroventral articulation facets bearing unique sets of concentric rail-like ridges and furrows. Supplementing the multiple-overlap chroniosuchian type articulation, the interlocking ridges and furrows confined the relative motion of two neighboring osteoderms to a rotation in slightly oblique and curved contact planes. Given the significant lateral narrowing of the dorsal ornamented non-overlap area, the horizontal component of the plate-to-plate rotation angles could reach up to 7.5◦, enabling more extensive lateral flexion of the trunk than in other chroniosuchids. Considering functional analogs, the chroniosuchian osteoderm system probably stabilized the vertebral column against shearing, torsion, tension, and compression loads and thus facilitated terrestrial locomotion at the expense of trunk flexibility. With its particular morphology, the carapace of M. pustulatus, however, was more suitable for locomotion styles featuring lateral body undulation than the carapaces of Permian chroniosuchids. We interpret this speciality as a secondary adaptation to an aquatic habitat.
Buchwitz, M. and S. Voigt. 2010. Peculiar carapace structure of a Triassic chroniosuchian implies evolutionary shift in trunk flexibility. Journal of Vertebrate Paleontology 30:1697-1708. DOI: 10.1080/02724634.2010.521685
Abstract - Dermal ossifications are widespread in Permian and Triassic tetrapods, but only members of the Chroniosuchia possess a series of dorsal osteoderms with a complex plate-to-plate articulation mechanism in addition to a contact between each osteoderm and its associated vertebral spine. The stratigraphically youngest chroniosuchid, Madygenerpeton pustulatus, from the Triassic of Kyrgyzstan provides new insight on the function of the chroniosuchian osteoderm system. Osteoderms of M. pustulatus are broad, peaked-roof-shaped to arched, with enlarged posterodorsal and anteroventral articulation facets bearing unique sets of concentric rail-like ridges and furrows. Supplementing the multiple-overlap chroniosuchian type articulation, the interlocking ridges and furrows confined the relative motion of two neighboring osteoderms to a rotation in slightly oblique and curved contact planes. Given the significant lateral narrowing of the dorsal ornamented non-overlap area, the horizontal component of the plate-to-plate rotation angles could reach up to 7.5◦, enabling more extensive lateral flexion of the trunk than in other chroniosuchids. Considering functional analogs, the chroniosuchian osteoderm system probably stabilized the vertebral column against shearing, torsion, tension, and compression loads and thus facilitated terrestrial locomotion at the expense of trunk flexibility. With its particular morphology, the carapace of M. pustulatus, however, was more suitable for locomotion styles featuring lateral body undulation than the carapaces of Permian chroniosuchids. We interpret this speciality as a secondary adaptation to an aquatic habitat.
Bentonyx sidensis, a new Rhynchosaur from the Middle Triassic of England
A note in the newest issue of the Journal of Vertebrate Paleontology reviews the type and referred material of the rhynchosaur Fodonyx spenceri and concludes that a referred skull actually belongs to a new taxon. This new taxon is named Bentonyx sidensis in honor of Professor Mike Benton of the University of Bristol, and authority on rhynchosaurs and a mentor to many students of the Triassic. You can read more about this is a recent post by David Hone, the third author on this paper.
I would like to congratulate Mike regarding this honor, especially in having the member of a taxon so dear to him named accordingly.
Langer, M. C. , Montefeltro, F. C. , Hone, D. E. , Whatley, R. and C. L. Schultz. 2010. On Fodonyx spenceri and a new rhynchosaur from the Middle Triassic of Devon. Journal of Vertebrate Paleontology 30:1884 — 1888. DOI: 10.1080/02724634.2010.521901
I would like to congratulate Mike regarding this honor, especially in having the member of a taxon so dear to him named accordingly.
Langer, M. C. , Montefeltro, F. C. , Hone, D. E. , Whatley, R. and C. L. Schultz. 2010. On Fodonyx spenceri and a new rhynchosaur from the Middle Triassic of Devon. Journal of Vertebrate Paleontology 30:1884 — 1888. DOI: 10.1080/02724634.2010.521901
Rainforest Collapse Triggered Carboniferous Tetrapod Diversification in Euramerica
A new paper that argues that ecosystem devestation in the Carboniferous provided conditions that led to increased diversity in amniotes and basically set the stage for the rise of archosaurs in the Mesozoic.
From Science Daily article: "Global warming devastated tropical rainforests 300 million years ago. Now scientists report the unexpected discovery that this event triggered an evolutionary burst among reptiles -- and inadvertently paved the way for the rise of dinosaurs, 100 million years later". Read more here.
Sahney, S., Benton, M. J., and H. J. Falcon-Lang. 2010. Rainforest collapse triggered Carboniferous tetrapod diversification in Euramerica. Geology 38: 1079-1082. DOI: 10.1130/G31182.1
Abstract - Abrupt collapse of the tropical rainforest biome (Coal Forests) drove rapid diversification of Carboniferous tetrapods (amphibians and reptiles) in Euramerica. This finding is based on analysis of global and alpha diversity databases in a precise geologic context. From Visean to Moscovian time, both diversity measures steadily increased, but following rainforest collapse in earliest Kasimovian time (ca. 305 Ma), tetrapod extinction rate peaked, alpha diversity imploded, and endemism developed for the first time. Analysis of ecological diversity shows that rainforest collapse was also accompanied by acquisition of new feeding strategies (predators, herbivores), consistent with tetrapod adaptation to the effects of habitat fragmentation and resource restriction. Effects on amphibians were particularly devastating, while amniotes (‘reptiles’) fared better, being ecologically adapted to the drier conditions that followed. Our results demonstrate, for the first time, that Coal Forest fragmentation influenced profoundly the ecology and evolution of terrestrial fauna in tropical Euramerica, and illustrate the tight coupling that existed between vegetation, climate, and trophic webs.
From Science Daily article: "Global warming devastated tropical rainforests 300 million years ago. Now scientists report the unexpected discovery that this event triggered an evolutionary burst among reptiles -- and inadvertently paved the way for the rise of dinosaurs, 100 million years later". Read more here.
Sahney, S., Benton, M. J., and H. J. Falcon-Lang. 2010. Rainforest collapse triggered Carboniferous tetrapod diversification in Euramerica. Geology 38: 1079-1082. DOI: 10.1130/G31182.1
Abstract - Abrupt collapse of the tropical rainforest biome (Coal Forests) drove rapid diversification of Carboniferous tetrapods (amphibians and reptiles) in Euramerica. This finding is based on analysis of global and alpha diversity databases in a precise geologic context. From Visean to Moscovian time, both diversity measures steadily increased, but following rainforest collapse in earliest Kasimovian time (ca. 305 Ma), tetrapod extinction rate peaked, alpha diversity imploded, and endemism developed for the first time. Analysis of ecological diversity shows that rainforest collapse was also accompanied by acquisition of new feeding strategies (predators, herbivores), consistent with tetrapod adaptation to the effects of habitat fragmentation and resource restriction. Effects on amphibians were particularly devastating, while amniotes (‘reptiles’) fared better, being ecologically adapted to the drier conditions that followed. Our results demonstrate, for the first time, that Coal Forest fragmentation influenced profoundly the ecology and evolution of terrestrial fauna in tropical Euramerica, and illustrate the tight coupling that existed between vegetation, climate, and trophic webs.
"Triassic Attack"
Unfortunately (or maybe not) I missed this movie, which aired in the U.S. last Saturday, about a Native American curse that causes roadside dinosaur attractions to come alive and eat everything. Despite being called "Triassic Attack" the main culprits are reportedly a Tyrannosaurus and a Cretaceous age pterosaur. Based on the previews and other comments it was probably pretty enjoyably horrible as a B-movie should be, but I am dissapointed that the producers didn't educate themselves a bit and use actual Triassic critters.
Did anyone see this and care to report?
Stratigraphic Correlations of Gondwanan Basins in India and the "Laurasian" Fauna of Northern Gondwana in the Late Triassic
Here is a fairly obscure, but interesting new paper providing updated correlations of strata (including that of Triassic age) in the Gondwanan Basins of India. The final paper could have benefited from some more editing, but overall it provides a decent synthesis and outlines some of the problems of correlations in this are of Gondwana. Most significant is that there are no absolute time constraints available for these strata because of the lack of datable volcanic materials. The overall climate for the entire Triassic for this area is given as arid with a key sea level regression in the Norian. Note, however, that the authors explicitly use the 2004 ISC timescale, and that under currently proposed revisions to this timescale the Carnian is more restricted.
The Triassic vertebrate fauna of India has always struck me as bizarre, mainly because the Early Triassic fauna is extremely similar to that of the Lystrosaurus assemblage zone of South Africa, and does contain several species of Lystrosaurus. Yet the Middle and Late Triassic fauna has much more of a Laurasian feel to it, especially the Late Triassic fauna, which includes basal phytosaurs such as Parasuchus, and more advanced phytosaurs such as a Leptosuchus-like form. Aetosaurs are represented by a paratypothoracisine form, which are only known from North America and Europe. Finally, metoposaurid temnospondyls are also common as in North America and Europe.
This seems very odd to me given that in paleogeographic reconstructions throughout the Triassic, India is firmly nestled on the western edge of modern day Africa, contacting Australia, and Antarctica, and separated from North America by all of northern Africa and from Europe by the Tethys. Unfortunately the Triassic fauna of North Africa is extremely sparse, although the Moroccan fauna is very similar to that of India and Laurasia. Perhaps Northern Africa served as a corridor for the Laurasian-type fauna, whereas there was some restriction from South America and South Africa in the Latest Triassic. Thus it seems that at this time there are not distinct Laurasian and Gondwanan distributions of tetrapods, but rather separate southern Gondwana and northern Gondwana/Laurasia distributions.
Mukhopadhyay, G., Mukhopadhyay, S. K., Roychowdhury, M., and P. K. Parui. 2010. Stratigraphic Correlation between Different Gondwana Basins of India.
Journal of the Geological Society of India 76:251-266. DOI: 10.1007/s12594-010-0097-6
Abstract - Gondwana Basins of India occur within the suture zones of Precambrian cratonic blocks of Peninsular India along some linear belts. More than 99% of the total coal resource of the country is present within these basins. The basins are demarcated by boundary faults having graben or half-graben geometry. These basins preserve a thick sedimentary pile deposited over nearly 200 million years from latest Carboniferous to Lower Cretaceous. However, due to lack of well-constrained data, age of most of the formations is assigned tentatively. This has resulted in diversified views on both intra- and inter-basinal stratigraphic correlation particularly in case of Upper Gondwana formations. It is well recognised that there are distinct spatial and temporal similarities in lithological, faunal and floral distribution in different Gondwana Basins of southern continents, including India, that were once part of supercontinent Gondwanaland. To address the problems of Indian Gondwana stratigraphy, during the present study, some unique events, also recognised in other parts of Gondwanaland, like marine flooding surfaces, large scale tectonic events or major change in depositional environment have been used as a tool for temporal correlation within the Gondwana Basins of India. Many of these events have been dated from different basins elsewhere. Considering these major events as time planes the total time span of deposition in Gondwana Basins has been classified into seven time slots. Recognition of these time planes helps in interbasinal correlation of different formations in Indian Gondwana basins and assigning the age, wherever available. This approach also helps in better understanding of basinal history. Unless otherwise mentioned, the time scale proposed by International Commission on Stratigraphy (2004) has been followed in this paper.
The Triassic vertebrate fauna of India has always struck me as bizarre, mainly because the Early Triassic fauna is extremely similar to that of the Lystrosaurus assemblage zone of South Africa, and does contain several species of Lystrosaurus. Yet the Middle and Late Triassic fauna has much more of a Laurasian feel to it, especially the Late Triassic fauna, which includes basal phytosaurs such as Parasuchus, and more advanced phytosaurs such as a Leptosuchus-like form. Aetosaurs are represented by a paratypothoracisine form, which are only known from North America and Europe. Finally, metoposaurid temnospondyls are also common as in North America and Europe.
This seems very odd to me given that in paleogeographic reconstructions throughout the Triassic, India is firmly nestled on the western edge of modern day Africa, contacting Australia, and Antarctica, and separated from North America by all of northern Africa and from Europe by the Tethys. Unfortunately the Triassic fauna of North Africa is extremely sparse, although the Moroccan fauna is very similar to that of India and Laurasia. Perhaps Northern Africa served as a corridor for the Laurasian-type fauna, whereas there was some restriction from South America and South Africa in the Latest Triassic. Thus it seems that at this time there are not distinct Laurasian and Gondwanan distributions of tetrapods, but rather separate southern Gondwana and northern Gondwana/Laurasia distributions.
Mukhopadhyay, G., Mukhopadhyay, S. K., Roychowdhury, M., and P. K. Parui. 2010. Stratigraphic Correlation between Different Gondwana Basins of India.
Journal of the Geological Society of India 76:251-266. DOI: 10.1007/s12594-010-0097-6
Abstract - Gondwana Basins of India occur within the suture zones of Precambrian cratonic blocks of Peninsular India along some linear belts. More than 99% of the total coal resource of the country is present within these basins. The basins are demarcated by boundary faults having graben or half-graben geometry. These basins preserve a thick sedimentary pile deposited over nearly 200 million years from latest Carboniferous to Lower Cretaceous. However, due to lack of well-constrained data, age of most of the formations is assigned tentatively. This has resulted in diversified views on both intra- and inter-basinal stratigraphic correlation particularly in case of Upper Gondwana formations. It is well recognised that there are distinct spatial and temporal similarities in lithological, faunal and floral distribution in different Gondwana Basins of southern continents, including India, that were once part of supercontinent Gondwanaland. To address the problems of Indian Gondwana stratigraphy, during the present study, some unique events, also recognised in other parts of Gondwanaland, like marine flooding surfaces, large scale tectonic events or major change in depositional environment have been used as a tool for temporal correlation within the Gondwana Basins of India. Many of these events have been dated from different basins elsewhere. Considering these major events as time planes the total time span of deposition in Gondwana Basins has been classified into seven time slots. Recognition of these time planes helps in interbasinal correlation of different formations in Indian Gondwana basins and assigning the age, wherever available. This approach also helps in better understanding of basinal history. Unless otherwise mentioned, the time scale proposed by International Commission on Stratigraphy (2004) has been followed in this paper.
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