You, H.-L., Azuma, Y., Wang, T., Wang, Y.-M., and Z.-M. Dong. 2014. The first well-preserved coelophysoid theropod dinosaur from Asia. Zootaxa 3873:233–249.
Abstract - Previously reported coelophysoid material from Asia (excluding the Gondwanan territory of India) is limited to two specimens that comprise only limb fragments. This paper describes a new genus and species of coelophysoid, Panguraptor lufengensis, from the Lower Jurassic Lufeng Formation of Yunnan Province, China. The new taxon is represented by a well-preserved skeleton, including the skull and lower jaw, the presacral vertebral column and partial ribs, the right scapula, a partial forelimb, part of the pelvic girdle, and an almost complete hind limb. It is distinguished from other coelophysoid theropods by the unique combination of the following three character states: 1) diagonal (rostrodorsal-caudoventral) ridge on lateral surface of maxilla, within antorbital fossa, 2) elliptical, laterally facing fenestra caudodorsal to aforementioned diagonal ridge, and 3) hooked craniomedial corner of distal tarsal IV. Cladistic analysis recovers Panguraptor lufengensis deeply nested within Coelophysoidea as a member of Coelophysidae, and it is more closely related to Coelophysis than to “Syntarsus”. Panguraptor represents the first well-preserved coelophysoid theropod dinosaur from Asia, and provides fresh evidence supporting the hypothesis that terrestrial tetrapods tended to be distributed pan-continentally during the Early Jurassic.
Showing posts with label Early Jurassic. Show all posts
Showing posts with label Early Jurassic. Show all posts
Tachiraptor admirabilis and the Early Dispersal of Dinosaurs after the end-Triassic Extinction
Langer, M. C., Rincón, A. D., Ramezani, J., Solórzano, A., and O. W. M. Rauhut. 2014. New dinosaur (Theropoda, stem-Averostra) from the earliest Jurassic of the La Quinta Formation,
Venezuelan Andes. Royal Society Open Science 1: 140184.
Venezuelan Andes. Royal Society Open Science 1: 140184.
http://dx.doi.org/10.1098/rsos.140184
Abstract - Dinosaur skeletal remains are almost unknown from northern South America. One of the few exceptions comes from a small outcrop in the northernmost extension of the Andes, along the
western border of Venezuela, where strata of the La Quinta Formation have yielded the ornithischian Laquintasaura venezuelae and other dinosaur remains. Here, we report isolated bones (ischium and tibia) of a small new theropod, Tachiraptor admirabilis gen. et sp. nov., which differs from all previously known members of the group by an unique suite of features of its tibial articulations. Comparative/phylogenetic studies place the new form as the sister taxon to Averostra, a theropod group that is known primarily from the Middle Jurassic onwards. A new U–Pb zircon date (isotope dilution thermal-ionization mass spectrometry; ID-TIMS method) from the bone bed matrix suggests an earliest Jurassic maximum age for the La Quinta Formation. A dispersal–vicariance analysis suggests that such a stratigraphic gap is more likely to be filled by new records from north and central Pangaea than from southern areas. Indeed, our data show that the sampled summer-wet equatorial belt, which yielded the new taxon, played a pivotal role in theropod evolution across the Triassic–Jurassic boundary
Tachiraptor admirabilis, a New Theropod Dinosaur from the Earliest Jurassic of Venezuela
The paper will be out on October 8th, but Science's website already has a news article up about the find. It is from the same locality as the early ornithischian dinosaur Laquintasaura, which was described earlier this year.
New Data on Small Theropod Footprints from Massachusetts
Dalman. S. G. 2012. New Data on Small Theropod Footprints from the Early Jurassic (Hettangian) Hartford Basin of Massachusetts, United States. Bulletin of the Peabody Museum of Natural History 53:333-353. doi:http://www.bioone.org/doi/abs/10.3374/014.053.0201
Abstract - A Portland Formation Lower Jurassic (Hettangian) dinosaur tracksite in Granby, Massachusetts, USA, has yielded a diverse dinosaur footprint assemblage. The tracksite preserves 140 theropod dinosaur footprints, ranging in length from 15 to 35 cm; the ichnofauna includes Anchisauripus, Eubrontes, Grallator and other extremely small theropod dinosaur footprints. The small tracks are compared with similar ichnites from the Lower Jurassic of western North America and central Poland. The small theropod footprints, which are described in detail, show some resemblance to the poorly known ichnogenus Stenonyx (Lull, 1904), which is considered an invalid ichnotaxon by many other workers. The footprints exhibit a distinct morphology of the metatarsophalangeal area, suggesting that these small ichnites are closely related to Kayentapus and Grallator. These small tracks are the first reported from the Hartford Basin of Granby, Massachusetts.
Abstract - A Portland Formation Lower Jurassic (Hettangian) dinosaur tracksite in Granby, Massachusetts, USA, has yielded a diverse dinosaur footprint assemblage. The tracksite preserves 140 theropod dinosaur footprints, ranging in length from 15 to 35 cm; the ichnofauna includes Anchisauripus, Eubrontes, Grallator and other extremely small theropod dinosaur footprints. The small tracks are compared with similar ichnites from the Lower Jurassic of western North America and central Poland. The small theropod footprints, which are described in detail, show some resemblance to the poorly known ichnogenus Stenonyx (Lull, 1904), which is considered an invalid ichnotaxon by many other workers. The footprints exhibit a distinct morphology of the metatarsophalangeal area, suggesting that these small ichnites are closely related to Kayentapus and Grallator. These small tracks are the first reported from the Hartford Basin of Granby, Massachusetts.
Neotype Proposal for Anchisaurus polyzelus
Galton, P.M. 2012. Case 3561 Anchisaurus Marsh, 1885 (Dinosauria, Sauropodomorpha): proposed conservation of usage by designation of a neotype for its type species Megadactylus polyzelus Hitchcock, 1865. Bulletin of Zoological Nomenclature 69 (1): 44-50.
Abstract - The purpose of this application, under Article 75.5 of the Code, is to conserve the usage of the name Anchisaurus Marsh, 1885 (Lower Jurassic, Connecticut Valley, northeastern U.S.A.) that is based on Megadactylus polyzelus Hitchcock, 1865. It is proposed to replace the fragmentary and non-diagnostic holotype of M. polyzelus with a diagnostic neotype, an almost complete skull and skeleton (YPM 1883, holotype of A. colurus Marsh, 1891). This specimen has formed the basis for the concept of Anchisaurus, the first basal sauropodomorph genus from the U.S.A. and still the best represented from there since it was illustrated by Marsh (1892, 1893), and of A. polyzelus since it was illustrated by Galton (1976). Anchisaurus is the basis for ANCHISAURIDAE Marsh, 1885, the first basal sauropodomorph family to be named, and for the Anchisauria Galton & Upchurch, 2004.
Oldest Known Dinosaurian Nesting Site
Here is the abstract and link to the article discussed in the linked news report from yesterday.
Reisz, R. R., Evans, D. C., Roberts, E. M., Sues, H.-D., and A. M. Yates. 2012. Oldest known dinosaurian nesting site and reproductive biology of the Early Jurassic sauropodomorph Massospondylus. PNAS online before print. DOI 10.1073/pnas.1109385109
Abstract - The extensive Early Jurassic continental strata of southern Africa have yielded an exceptional record of dinosaurs that includes scores of partial to complete skeletons of the sauropodomorph Massospondylus, ranging from embryos to large adults. In 1976 an incomplete egg clutch including in ovo embryos of this dinosaur, the oldest known example in the fossil record, was collected from a road-cut talus, but its exact provenance was uncertain. An excavation program at the site started in 2006 has yielded multiple in situ egg clutches, documenting the oldest known dinosaurian nesting site, predating other similar sites by more than 100 million years. The presence of numerous clutches of eggs, some of which contain embryonic remains, in at least four distinct horizons within a small area, provides the earliest known evidence of complex reproductive behavior including site fidelity and colonial nesting in a terrestrial vertebrate. Thus, fossil and sedimentological evidence from this nesting site provides empirical data on reproductive strategies in early dinosaurs. A temporally calibrated optimization of dinosaurian reproductive biology not only demonstrates the primary significance of the Massospondylus nesting site, but also provides additional insights into the initial stages of the evolutionary history of dinosaurs, including evidence that deposition of eggs in a tightly organized single layer in a nest evolved independently from brooding.
Fossil Evidence on Origin of the Mammalian Brain.
Rowe, T., Macrini, T. E., and Z.-X. Luo. 2011. Fossil Evidence on Origin of the Mammalian Brain. Science 332:955. DOI: 10.1126/science.1203117 [supp. info]
Abstract - Many hypotheses have been postulated regarding the early evolution of the mammalian brain. Here, x-ray tomography of the Early Jurassic mammaliaforms Morganucodon and Hadrocodium sheds light on this history. We found that relative brain size expanded to mammalian levels, with enlarged olfactory bulbs, neocortex, olfactory (pyriform) cortex, and cerebellum, in two evolutionary pulses. The initial pulse was probably driven by increased resolution in olfaction and improvements in tactile sensitivity (from body hair) and neuromuscular coordination. A second pulse of olfactory enhancement then enlarged the brain to mammalian levels. The origin of crown Mammalia saw a third pulse of olfactory enhancement, with ossified ethmoid turbinals supporting an expansive olfactory epithelium in the nasal cavity, allowing full expression of a huge odorant receptor genome.
Abstract - Many hypotheses have been postulated regarding the early evolution of the mammalian brain. Here, x-ray tomography of the Early Jurassic mammaliaforms Morganucodon and Hadrocodium sheds light on this history. We found that relative brain size expanded to mammalian levels, with enlarged olfactory bulbs, neocortex, olfactory (pyriform) cortex, and cerebellum, in two evolutionary pulses. The initial pulse was probably driven by increased resolution in olfaction and improvements in tactile sensitivity (from body hair) and neuromuscular coordination. A second pulse of olfactory enhancement then enlarged the brain to mammalian levels. The origin of crown Mammalia saw a third pulse of olfactory enhancement, with ossified ethmoid turbinals supporting an expansive olfactory epithelium in the nasal cavity, allowing full expression of a huge odorant receptor genome.
New Skull Description of the Early Jurassic Ornithischian Dinosaur Heterodontosaurus tucki
Norman, D. B., Crompton, A. W., Butler, R. J., Porro, L. B., and A. J. Charig. 2011. The Lower Jurassic ornithischian dinosaur Heterodontosaurus tucki Crompton & Charig, 1962: cranial anatomy, functional morphology, taxonomy, and relationships. Zoological Journal of the Linnaean Society published first online 20 May 2011. DOI: 10.1111/j.1096-3642.2011.00697.x
Abstract - The cranial anatomy of the Lower Jurassic ornithischian dinosaur Heterodontosaurus tucki Crompton & Charig, 1962 is described in detail for the first time on the basis of two principal specimens: the holotype (SAM-PK-K337) and referred skull (SAM-PK-K1332). In addition several other specimens that have a bearing on the interpretation of the anatomy and biology of Heterodontosaurus are described. The skull and lower jaw of Heterodontosaurus are compact and robust but perhaps most notable for the heterodont dentition that merited the generic name. Details of the cranial anatomy are revealed and show that the skull is unexpectedly specialized in such an early representative of the Ornithischia, including: the closely packed, hypsodont crowns and ‘warping’ of the occlusal surfaces (created by progressive variation in the angulation of wear on successive crowns) seen in the cheek dentition; the unusual sutural relationships between the bones along the dorsal edge of the lower jaw; the very narrow, deeply vaulted palate and associated structures on the side wall of the braincase; and the indications of cranial pneumatism (more commonly seen in basal archosaurs and saurischian dinosaurs). Evidence for tooth replacement (which has long been recognized, despite frequent statements to the contrary) is suggestive of an episodic, rather than continuous, style of tooth replacement that is, yet again, unusual in diapsids generally and particularly so amongst ornithischian dinosaurs. Cranial musculature has been reconstructed and seems to conform to that typically seen in diapsids, with the exception of the encroachment of M. adductor mandibulae externus superficialis across the lateral surface of the temporal region and external surface of the lower jaw. Indications, taken from the unusual shape of the occlusal surfaces of the cheek dentition and jaw musculature, are suggestive of a novel form of jaw action in this dinosaur. The taxonomy of currently known late Karoo-aged heterodontosaurids from southern Africa is reviewed. Although complicated by the inadequate nature of much of the known material, it is concluded that two taxa may be readily recognized: H. tucki and Abrictosaurus consors. At least one additional taxon is recognized within the taxa presently named Lanasaurus and Lycorhinus; however, both remain taxonomically problematic and their status needs to be further tested and may only be resolved by future discoveries. The only other named taxon, Geranosaurus atavus, represents an invalid name. The recognition of at least four distinct taxa indicates that the heterodontosaurids were speciose within the late Karoo ecosystem. The systematics of Heterodontosaurus and its congeners has been analysed, using a restricted sample of taxa. A basal (nongenasaurian) position within Ornithischia is re-affirmed. There are at least four competing hypotheses concerning the phylogenetic placement of the Heterodontosauridae, so the evidence in support of the various hypotheses is reviewed in some detail. At present the best-supported hypothesis is the one which places Heterodontosauridae in a basal (non-genasaurian) position; however, the evidence is not fully conclusive and further information is still needed in respect of the anatomy of proximate outgroups, as well as more complete anatomical details for other heterodontosaurids. Heterodontosaurids were not such rare components of the late Karoo ecosystem as previously thought; evidence also suggests that from a phylogenetic perspective they occupied a potentially crucial position during the earliest phases of ornithischian dinosaur evolution.
Abstract - The cranial anatomy of the Lower Jurassic ornithischian dinosaur Heterodontosaurus tucki Crompton & Charig, 1962 is described in detail for the first time on the basis of two principal specimens: the holotype (SAM-PK-K337) and referred skull (SAM-PK-K1332). In addition several other specimens that have a bearing on the interpretation of the anatomy and biology of Heterodontosaurus are described. The skull and lower jaw of Heterodontosaurus are compact and robust but perhaps most notable for the heterodont dentition that merited the generic name. Details of the cranial anatomy are revealed and show that the skull is unexpectedly specialized in such an early representative of the Ornithischia, including: the closely packed, hypsodont crowns and ‘warping’ of the occlusal surfaces (created by progressive variation in the angulation of wear on successive crowns) seen in the cheek dentition; the unusual sutural relationships between the bones along the dorsal edge of the lower jaw; the very narrow, deeply vaulted palate and associated structures on the side wall of the braincase; and the indications of cranial pneumatism (more commonly seen in basal archosaurs and saurischian dinosaurs). Evidence for tooth replacement (which has long been recognized, despite frequent statements to the contrary) is suggestive of an episodic, rather than continuous, style of tooth replacement that is, yet again, unusual in diapsids generally and particularly so amongst ornithischian dinosaurs. Cranial musculature has been reconstructed and seems to conform to that typically seen in diapsids, with the exception of the encroachment of M. adductor mandibulae externus superficialis across the lateral surface of the temporal region and external surface of the lower jaw. Indications, taken from the unusual shape of the occlusal surfaces of the cheek dentition and jaw musculature, are suggestive of a novel form of jaw action in this dinosaur. The taxonomy of currently known late Karoo-aged heterodontosaurids from southern Africa is reviewed. Although complicated by the inadequate nature of much of the known material, it is concluded that two taxa may be readily recognized: H. tucki and Abrictosaurus consors. At least one additional taxon is recognized within the taxa presently named Lanasaurus and Lycorhinus; however, both remain taxonomically problematic and their status needs to be further tested and may only be resolved by future discoveries. The only other named taxon, Geranosaurus atavus, represents an invalid name. The recognition of at least four distinct taxa indicates that the heterodontosaurids were speciose within the late Karoo ecosystem. The systematics of Heterodontosaurus and its congeners has been analysed, using a restricted sample of taxa. A basal (nongenasaurian) position within Ornithischia is re-affirmed. There are at least four competing hypotheses concerning the phylogenetic placement of the Heterodontosauridae, so the evidence in support of the various hypotheses is reviewed in some detail. At present the best-supported hypothesis is the one which places Heterodontosauridae in a basal (non-genasaurian) position; however, the evidence is not fully conclusive and further information is still needed in respect of the anatomy of proximate outgroups, as well as more complete anatomical details for other heterodontosaurids. Heterodontosaurids were not such rare components of the late Karoo ecosystem as previously thought; evidence also suggests that from a phylogenetic perspective they occupied a potentially crucial position during the earliest phases of ornithischian dinosaur evolution.
Arcusaurus pereirabdalorum, A New Basal Sauropodomorph From The Early Jurassic Of South Africa
Yates, A. M., Bonnan, M. F., and J. Neveling. 2011. A new basal sauropodomorph dinosaur from the Early Jurassic of South Africa. Journal of Vertebrate Paleontology 31:610-625. DOI: 10.1080/02724634.2011.560626
Abstract - A new basal sauropodomorph dinosaur, Arcusaurus pereirabdalorum, sp. nov., is named and described on the basis of a partial, disarticulated but associated skull and dispersed cranial and postcranial elements from at least two individuals. Arcusaurus is part of a distinctive local fauna from the upper Elliot Formation (Lower Jurassic) in the Senekal District, Free State, South Africa. It can be diagnosed by various details of the premaxilla, nasal, and dentary in the skull and the shape of the distal caudal vertebrae. The taxon displays an unusual mix of characteristics. It lacks several synapomorphies of Plateosauria (Plateosaurus + Massospondylus and all descendants of their most recent common ancestor) but does display other derived characteristics that are otherwise known only from less inclusive clades within Plateosauria. In a cladistic analysis a position outside Plateosauria as the sister group of the clade of Efraasia + more-derived sauropodomorphs is supported; however, this position was not found to be a significantly better explanation of the data as a relatively derived position within Plateosauria. If the basal position for Arcusaurus is accepted, then a divergence from other sauropodomorphs in the middle Norian and a ghost lineage up to 35 Ma is implied. No other non-plateosaurian sauropodomorphs are known from the Jurassic, making Arcusaurus a potentially relictual taxon in the Early Jurassic.
Abstract - A new basal sauropodomorph dinosaur, Arcusaurus pereirabdalorum, sp. nov., is named and described on the basis of a partial, disarticulated but associated skull and dispersed cranial and postcranial elements from at least two individuals. Arcusaurus is part of a distinctive local fauna from the upper Elliot Formation (Lower Jurassic) in the Senekal District, Free State, South Africa. It can be diagnosed by various details of the premaxilla, nasal, and dentary in the skull and the shape of the distal caudal vertebrae. The taxon displays an unusual mix of characteristics. It lacks several synapomorphies of Plateosauria (Plateosaurus + Massospondylus and all descendants of their most recent common ancestor) but does display other derived characteristics that are otherwise known only from less inclusive clades within Plateosauria. In a cladistic analysis a position outside Plateosauria as the sister group of the clade of Efraasia + more-derived sauropodomorphs is supported; however, this position was not found to be a significantly better explanation of the data as a relatively derived position within Plateosauria. If the basal position for Arcusaurus is accepted, then a divergence from other sauropodomorphs in the middle Norian and a ghost lineage up to 35 Ma is implied. No other non-plateosaurian sauropodomorphs are known from the Jurassic, making Arcusaurus a potentially relictual taxon in the Early Jurassic.
Neotype Designation for the Early Jurassic Sauropodomorph Massospondylus carinatus
Adam Yates has a new post over at his blog Dracovenator, regarding the status of the type specimen of Massospondylus carinatus, and mentions this new paper that provides a neotype designation for this taxon. Unfortunately the Palaeontologia Africana website is woefully out of date and therefore I cannot provide an abstract or a link to this article.
Yates, A. M. and Barrett, P. M. 2011 (for 2010). Massospondylus carinatus Owen 1854 (Dinosauria, Sauropodomorpha): proposed conservation of usage by designation of a neotype. Palaeontologia Africana 45: 7-10.
Yates, A. M. and Barrett, P. M. 2011 (for 2010). Massospondylus carinatus Owen 1854 (Dinosauria, Sauropodomorpha): proposed conservation of usage by designation of a neotype. Palaeontologia Africana 45: 7-10.
Chuxiongosaurus lufengensis, a New Basal Sauropod from the Early Jurassic of China
Lü J., Y. Kobayashi, Li T. & Zhong S., 2010. A new basal sauropod dinosaur from the Lufeng Basin, Yunnan Province, southwestern China. Acta Geologica Sinica 84: 1336-1342.
Abstract - A new dinosaur Chuxiongosaurus lufengensis gen. et sp. nov. is erected based on a nearly complete skull. The taxon is characterized by the lacrimal perpendicular to the ventral margin of the upper jaw, which is similar to that of Thecodontosaurus; a depression present on the dorsal profile of the snout behind the naris; the rostral profile of the maxilla slopes continuously towards the rostral tip; and the presence of 25 dentary teeth. It also displays prosauropod characters such as a relatively long skull, the slope of the maxillary rostral profile, and teeth that do not have basically constricted crowns. The new specimen is more basal than Anchisaurus and represents the first basal sauropod dinosaur from the Early Jurassic of China.
Abstract - A new dinosaur Chuxiongosaurus lufengensis gen. et sp. nov. is erected based on a nearly complete skull. The taxon is characterized by the lacrimal perpendicular to the ventral margin of the upper jaw, which is similar to that of Thecodontosaurus; a depression present on the dorsal profile of the snout behind the naris; the rostral profile of the maxilla slopes continuously towards the rostral tip; and the presence of 25 dentary teeth. It also displays prosauropod characters such as a relatively long skull, the slope of the maxillary rostral profile, and teeth that do not have basically constricted crowns. The new specimen is more basal than Anchisaurus and represents the first basal sauropod dinosaur from the Early Jurassic of China.
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.
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.
Upcoming Article on Massospondylus (Sauropodomorpha) Embryos from the Lower Jurassic of Africa
A bunch of news articles have come out over the last two days discussing an upcoming article in the Journal of Vertebrate Paleontology discussing details of embrionic remains of the Jurassic sauropodomorph Massospondylus.
At this time it is unclear how this paper will differ from the original find of Massospondylus embryos in 2005.
You can check out two of the new stories (including photos) here and here.
At this time it is unclear how this paper will differ from the original find of Massospondylus embryos in 2005.
You can check out two of the new stories (including photos) here and here.
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| from http://www.msnbc.msn.com/id/40133043/ns/technology_and_science-science/ |
Preview of New Early Jurassic "Coelophysoid" Fossil from China
This is a link to an article discussing new finds of "coelophysoid" material from Lufeng.
http://english.peopledaily.com.cn/90001/90782/7161153.html
Photos of the new material can be seen here. Pretty impressive!
http://www.cnr.cn/newscenter/xwtz/201010/t20101008_507139251.html#javascript_intro
Added 9 pm 10/9/2010: Looking at this a bit closer now that I have some time... I'm not convinced it is coelophysoid. The snout is too short and the face isn't "pointed" enough. There is a short-snouted form of "Coelophysis" out of the Coelophysis quarry that was mentioned by David Smith in a 2006 paper (I don't have the ref right now), but this also appears to be different than that. Rather this appears to be some kind of basal theropod, which would be very interesting out of an Early Jurassic deposit.
http://english.peopledaily.com.cn/90001/90782/7161153.html
Photos of the new material can be seen here. Pretty impressive!
http://www.cnr.cn/newscenter/xwtz/201010/t20101008_507139251.html#javascript_intro
Added 9 pm 10/9/2010: Looking at this a bit closer now that I have some time... I'm not convinced it is coelophysoid. The snout is too short and the face isn't "pointed" enough. There is a short-snouted form of "Coelophysis" out of the Coelophysis quarry that was mentioned by David Smith in a 2006 paper (I don't have the ref right now), but this also appears to be different than that. Rather this appears to be some kind of basal theropod, which would be very interesting out of an Early Jurassic deposit.
Dispersal as a Key Factor in Early Dinosaur Diversification of North America and the Myth of a 'Cosmopolitan' Dinosaur Fauna in the Early Mesozoic
New and available free from the Royal Society website. Popular news story here.
Rowe, T. B., Sues, H.-D., and R. Reisz. 2010. Dispersal and diversity in the earliest North American sauropodomorph dinosaurs, with a description of a new taxon. Proceedings of the Royal Society B, First Cite. doi:10.1098/rspb.2010.1867
Abstract - Sauropodomorph dinosaurs originated in the Southern Hemisphere in the Middle or Late Triassic and are commonly portrayed as spreading rapidly to all corners of Pangaea as part of a uniform Late Triassic to Early Jurassic cosmopolitan dinosaur fauna. Under this model, dispersal allegedly inhibited dinosaurian diversification, while vicariance and local extinction enhanced it. However, apomorphy-based analyses of the known fossil record indicate that sauropodomorphs were absent in North America until the Early Jurassic, reframing the temporal context of their arrival. We describe a new taxon from the Kayenta Formation of Arizona that comprises the third diagnosable sauropodomorph from the Early Jurassic of North America. We analysed its relationships to test whether sauropodomorphs reached North America in a single sweepstakes event or in separate dispersals. Our finding of separate arrivals by all three taxa suggests dispersal as a chief factor in dinosaurian diversification during at least the early Mesozoic. It questions whether a ‘cosmopolitan’ dinosaur fauna ever existed, and corroborates that vicariance, extinction and dispersal did not operate uniformly in time or under uniform conditions during the Mesozoic. Their relative importance is best measured in narrow time slices and circumscribed geographical regions.
Rowe, T. B., Sues, H.-D., and R. Reisz. 2010. Dispersal and diversity in the earliest North American sauropodomorph dinosaurs, with a description of a new taxon. Proceedings of the Royal Society B, First Cite. doi:10.1098/rspb.2010.1867
Abstract - Sauropodomorph dinosaurs originated in the Southern Hemisphere in the Middle or Late Triassic and are commonly portrayed as spreading rapidly to all corners of Pangaea as part of a uniform Late Triassic to Early Jurassic cosmopolitan dinosaur fauna. Under this model, dispersal allegedly inhibited dinosaurian diversification, while vicariance and local extinction enhanced it. However, apomorphy-based analyses of the known fossil record indicate that sauropodomorphs were absent in North America until the Early Jurassic, reframing the temporal context of their arrival. We describe a new taxon from the Kayenta Formation of Arizona that comprises the third diagnosable sauropodomorph from the Early Jurassic of North America. We analysed its relationships to test whether sauropodomorphs reached North America in a single sweepstakes event or in separate dispersals. Our finding of separate arrivals by all three taxa suggests dispersal as a chief factor in dinosaurian diversification during at least the early Mesozoic. It questions whether a ‘cosmopolitan’ dinosaur fauna ever existed, and corroborates that vicariance, extinction and dispersal did not operate uniformly in time or under uniform conditions during the Mesozoic. Their relative importance is best measured in narrow time slices and circumscribed geographical regions.
Tonganosaurus hei A New Sauropod from the Lower Jurassic of China
Li, K.Yang C.-Y., Liu, J., and Wang, Z.-X. 2010. A new sauropod from the Lower Jurassic of , Sichuan, China. Vertebrata PalAsiatica 48:185-202.
Huili
Abstract - A new sauropod, Tonganosaurus hei gen. et sp. nov. from the Yimen Formation (Lower Jurassic) of Sichuan, China, is described on the basis of a collection of bones. These fossils include about 20 vertebrae, a complete right pectoral girdle and right forelimb, the distal end of a left scapula, a pair of complete ischia, a somplete right hindlimb, the proximal and distal ends of a left femur, right metatarsals (mt. I, II, III, and V), a right pedal ungual, and ten neural spine and rib fragments. The third cervical and anterial caudals are most similar in shape to those of the mamenchisaurid Omeisaurus (from the Middle Jurassic, Sichuan Basin), and quite different from those of other sauropods. The material was therefore assigned to the Family Mamenchisauridae Young & Chao, 1972 and a new genus and species were established. This represents the first discovery of a sauropod in the Lower Jurassic of China since Gongxianosaurus was found in Sichuan Basin. The Tonganosaurus material is of great importance for understanding the phylogenetics of the early Sauropoda.
Huili
Abstract - A new sauropod, Tonganosaurus hei gen. et sp. nov. from the Yimen Formation (Lower Jurassic) of Sichuan, China, is described on the basis of a collection of bones. These fossils include about 20 vertebrae, a complete right pectoral girdle and right forelimb, the distal end of a left scapula, a pair of complete ischia, a somplete right hindlimb, the proximal and distal ends of a left femur, right metatarsals (mt. I, II, III, and V), a right pedal ungual, and ten neural spine and rib fragments. The third cervical and anterial caudals are most similar in shape to those of the mamenchisaurid Omeisaurus (from the Middle Jurassic, Sichuan Basin), and quite different from those of other sauropods. The material was therefore assigned to the Family Mamenchisauridae Young & Chao, 1972 and a new genus and species were established. This represents the first discovery of a sauropod in the Lower Jurassic of China since Gongxianosaurus was found in Sichuan Basin. The Tonganosaurus material is of great importance for understanding the phylogenetics of the early Sauropoda.
Revision of the Basal Sauropodomorph Anchisaurus polyzelus
This is the latest paper in the ongoing debate regarding the taxonomic validity of Anchisaurus polyzelus (Sauropodomorpha: Anchisauria) and the referral of three other partial specimens from the Early Jurassic Portland Formation of Massachusetts and Connecticut. Whereas, all workers now agree that the four specimens all belong to the same species, the debate has centered around the status of the type materials of A. polyzelus, because if they are not diagnostic, the next available name for this material is Ammosaurus major. Through reanalysis of the material Yates proposes seven autapomorphies diagnosing this material, including one of these also found in the holotype specimen of A. polyzelus. Thus, Yates argues that A. polyzelus is valid, all four specimens can unambiguously be referred to it, and that Ammosaurus major is the junior synonym. This paper also features a revised phylogentic analysis of the sauropodomorpha based on the reanalysis including repreparation of the skull found in one of the referred specimens. Anchisaurus is recovered at the base of Anchisauria and outside of Sauropoda.
As this is about the 6th paper in a little more than a decade dealing with this, I am awaiting the next installment ;).
Yates, A. M. in press. A revision of the problematic sauropodomorph dinosaurs from Manchester, Connecticut and the status of Anchisaurus Marsh. Palaeontology. doi: 10.1111/j.1475-4983.2010.00952.x
Abstract: The taxonomic status of the sauropodomorph dinosaurs from the Newark Supergroup of north-eastern USA is reviewed. The inclusion of the three articulated skeletons from Wolcott’s Quarry, Manchester, Connecticut in a single species is supported. Despite claims to the contrary the Manchester skeletons can be referred to the species Anchisaurus polyzelus, which is based on a fragmentary specimen from Massachusetts. Two autapomorphies: dorsoventrally flattened ischial blades set at a low angle to each other and slender sacral ribs of the first sacral vertebra, link the holotype of A. polyzelus to the Manchester specimens. A revised diagnosis of the species and new skull reconstruction are presented. Recent anatomical observations of A. polyzelus indicate that several character states used to assess its phylogenetic position require revision. However, these are not sufficient to overturn previous cladistic analyses. A revised cladistic analysis continues to find support for Anchisaurus as a relatively derived basal sauropodomorph that lies outside of the clade Melanorosaurus + Sauropoda but is more closely related to it than to ‘core prosauropods’ such as Plateosaurus and Massospondylus.
As this is about the 6th paper in a little more than a decade dealing with this, I am awaiting the next installment ;).
Yates, A. M. in press. A revision of the problematic sauropodomorph dinosaurs from Manchester, Connecticut and the status of Anchisaurus Marsh. Palaeontology. doi: 10.1111/j.1475-4983.2010.00952.x
Abstract: The taxonomic status of the sauropodomorph dinosaurs from the Newark Supergroup of north-eastern USA is reviewed. The inclusion of the three articulated skeletons from Wolcott’s Quarry, Manchester, Connecticut in a single species is supported. Despite claims to the contrary the Manchester skeletons can be referred to the species Anchisaurus polyzelus, which is based on a fragmentary specimen from Massachusetts. Two autapomorphies: dorsoventrally flattened ischial blades set at a low angle to each other and slender sacral ribs of the first sacral vertebra, link the holotype of A. polyzelus to the Manchester specimens. A revised diagnosis of the species and new skull reconstruction are presented. Recent anatomical observations of A. polyzelus indicate that several character states used to assess its phylogenetic position require revision. However, these are not sufficient to overturn previous cladistic analyses. A revised cladistic analysis continues to find support for Anchisaurus as a relatively derived basal sauropodomorph that lies outside of the clade Melanorosaurus + Sauropoda but is more closely related to it than to ‘core prosauropods’ such as Plateosaurus and Massospondylus.
Trio of New Early Jurassic Sauropodomorph Dinosaur Papers
Sertich, J. J. W., and M. A. Loewen. 2010. A New Basal Sauropodomorph Dinosaur from the Lower Jurassic Navajo Sandstone of Southern Utah. PLoS ONE 5(3): e9789. doi:10.1371/journal.pone.0009789
Abstract
Background: Basal sauropodomorphs, or ‘prosauropods,’ are a globally widespread paraphyletic assemblage of terrestrial herbivorous dinosaurs from the Late Triassic and Early Jurassic. In contrast to several other landmasses, the North American record of sauropodomorphs during this time interval remains sparse, limited to Early Jurassic occurrences of a single well known taxon from eastern North America and several fragmentary specimens from western North America.
Methodology/Principal Findings: On the basis of a partial skeleton, we describe here a new basal sauropodomorph dinosaur from the Lower Jurassic Navajo Sandstone of southern Utah, Seitaad ruessi gen. et sp. nov. The partially articulated skeleton of Seitaad was likely buried post-mortem in the base of a collapsed dune foreset. The new taxon is characterized by a plate-like medial process of the scapula, a prominent proximal expansion of the deltopectoral crest of the humerus, a strongly inclined distal articular surface of the radius, and a proximally and laterally hypertrophied proximal metacarpal I.
Conclusions/Significance: Phylogenetic analysis recovers Seitaad as a derived basal sauropodomorph closely related to plateosaurid or massospondylid ‘prosauropods’ and its presence in western North America is not unexpected for a member of this highly cosmopolitan clade. This occurrence represents one of the most complete vertebrate body fossil specimens yet recovered from the Navajo Sandstone and one of the few basal sauropodomorph taxa currently known from North America.
Knoll, F. 2010. A primitive sauropodomorph from the upper Elliot Formation of Lesotho. Geological Magazine early online doi:10.1017/S001675681000018X
Abstract – A well-preserved, articulated dinosaur skeleton from southern Africa is described. The specimen comes from the upper Elliot Formation (?Hettangian) of Ha Ralekoala (Lesotho) and represents a new species: Ignavusaurus rachelis genus et species nova. A cladistic analysis suggests that Ignavusaurus is more derived than Thecodontosaurus–Pantydraco, but more primitive than Efraasia. Ignavusaurus indeed shares a number of unambiguous synapomorphies with the taxa more derived than Thecodontosaurus–Pantydraco, such as a fully open acetabulum, but it is more plesiomorphic than Efraasia and more derived sauropodomorphs as shown by the evidence of, for instance, the distal extremity of its tibia that is is longer (cranio-caudally) than wide (latero-medially). The discovery of Ignavusaurus increases the known diversity of the early sauropodomorph fauna of the upper Elliot
Formation, which stands as one of the richest horizons in the world in this respect.
Bandyopadhyay, S., Gillette, D. D., Ray, S., and D. P. Sengupta. 2010. Osteology of Barapasaurus tagorei (Dinosauria: Sauropoda) from the Early Jurassic of India.
Palaeontology early online doi: 10.1111/j.1475-4983.2010.00933.x
Abstract - The sauropod dinosaur, Barapasaurus tagorei, is known from the Early Jurassic Kota Formation (Sinemurian to Pliensbachian) of India. The taxon is represented by c. 300 bones that were found associated with large fossilized tree trunks and were collected from the interface of sandstone and mudstone units covering an area of c. 276 meters squared. The collection includes one partial skeleton; most of the remainder of the bones were disarticulated, disassociated and dispersed, but taphonomic analysis permits recognition of associated elements comprising several individuals. Skeletal anatomy of Barapasaurus includes several teeth, vertebrae from the caudal cervicals rearward to the terminal caudals, and most elements of the appendicular skeleton. Barapasaurus is characterized by spoon-shaped teeth with bulbous bases and grooves on the anterolabial and posterolingual sides of the crown, coarse tubercles on the carina, acamerate cranial and dorsal vertebrae, lateral laminae of the middle and caudal dorsal neural spines composed of spinodiapophyseal and spinopostzygapophyseal laminae, neural canal of the mid-dorsal vertebrae opens dorsally through a narrow slit into a large cavity and sacrum with four co-ossified vertebrae. Phylogenetic analysis reveals that Barapasaurus is basal in comparison with Vulcanodon and is removed from Eusauropoda.
Abstract
Background: Basal sauropodomorphs, or ‘prosauropods,’ are a globally widespread paraphyletic assemblage of terrestrial herbivorous dinosaurs from the Late Triassic and Early Jurassic. In contrast to several other landmasses, the North American record of sauropodomorphs during this time interval remains sparse, limited to Early Jurassic occurrences of a single well known taxon from eastern North America and several fragmentary specimens from western North America.
Methodology/Principal Findings: On the basis of a partial skeleton, we describe here a new basal sauropodomorph dinosaur from the Lower Jurassic Navajo Sandstone of southern Utah, Seitaad ruessi gen. et sp. nov. The partially articulated skeleton of Seitaad was likely buried post-mortem in the base of a collapsed dune foreset. The new taxon is characterized by a plate-like medial process of the scapula, a prominent proximal expansion of the deltopectoral crest of the humerus, a strongly inclined distal articular surface of the radius, and a proximally and laterally hypertrophied proximal metacarpal I.
Conclusions/Significance: Phylogenetic analysis recovers Seitaad as a derived basal sauropodomorph closely related to plateosaurid or massospondylid ‘prosauropods’ and its presence in western North America is not unexpected for a member of this highly cosmopolitan clade. This occurrence represents one of the most complete vertebrate body fossil specimens yet recovered from the Navajo Sandstone and one of the few basal sauropodomorph taxa currently known from North America.
Knoll, F. 2010. A primitive sauropodomorph from the upper Elliot Formation of Lesotho. Geological Magazine early online doi:10.1017/S001675681000018X
Abstract – A well-preserved, articulated dinosaur skeleton from southern Africa is described. The specimen comes from the upper Elliot Formation (?Hettangian) of Ha Ralekoala (Lesotho) and represents a new species: Ignavusaurus rachelis genus et species nova. A cladistic analysis suggests that Ignavusaurus is more derived than Thecodontosaurus–Pantydraco, but more primitive than Efraasia. Ignavusaurus indeed shares a number of unambiguous synapomorphies with the taxa more derived than Thecodontosaurus–Pantydraco, such as a fully open acetabulum, but it is more plesiomorphic than Efraasia and more derived sauropodomorphs as shown by the evidence of, for instance, the distal extremity of its tibia that is is longer (cranio-caudally) than wide (latero-medially). The discovery of Ignavusaurus increases the known diversity of the early sauropodomorph fauna of the upper Elliot
Formation, which stands as one of the richest horizons in the world in this respect.
Bandyopadhyay, S., Gillette, D. D., Ray, S., and D. P. Sengupta. 2010. Osteology of Barapasaurus tagorei (Dinosauria: Sauropoda) from the Early Jurassic of India.
Palaeontology early online doi: 10.1111/j.1475-4983.2010.00933.x
Abstract - The sauropod dinosaur, Barapasaurus tagorei, is known from the Early Jurassic Kota Formation (Sinemurian to Pliensbachian) of India. The taxon is represented by c. 300 bones that were found associated with large fossilized tree trunks and were collected from the interface of sandstone and mudstone units covering an area of c. 276 meters squared. The collection includes one partial skeleton; most of the remainder of the bones were disarticulated, disassociated and dispersed, but taphonomic analysis permits recognition of associated elements comprising several individuals. Skeletal anatomy of Barapasaurus includes several teeth, vertebrae from the caudal cervicals rearward to the terminal caudals, and most elements of the appendicular skeleton. Barapasaurus is characterized by spoon-shaped teeth with bulbous bases and grooves on the anterolabial and posterolingual sides of the crown, coarse tubercles on the carina, acamerate cranial and dorsal vertebrae, lateral laminae of the middle and caudal dorsal neural spines composed of spinodiapophyseal and spinopostzygapophyseal laminae, neural canal of the mid-dorsal vertebrae opens dorsally through a narrow slit into a large cavity and sacrum with four co-ossified vertebrae. Phylogenetic analysis reveals that Barapasaurus is basal in comparison with Vulcanodon and is removed from Eusauropoda.
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