In the conclusions section of the recent paper by Kammerer et al., there is a worthwhile discussion regarding the taxonomic assignment of isolated Triassic teeth. In the past some isolated leaf-shaped, denticulated teeth were considered apomorphic and used to erect discrete ornithischian dinosaur taxa (e.g., Hunt and Lucas, 1994; Heckert, 2004). Parker et al. (2005) argued that at least in Revueltosaurus callenderi, the teeth were apomorphic allowing assignment of non-dental material to the taxon. Irmis et al. (2007) discussed this in more detail, arguing the teeth of other purported ornithischians were not assignable to dinosaurs based solely on morphology and in fact could not be assigned to a more inclusive taxonomic level than Archosauromorpha.
However, in this recent paper Kammerer et al. note that many of these Triassic tooth taxa are very similar to the teeth of the traversodontid cynodonts Dadadon isaloi and Arctotraversodon plemmyridon. They especially note that the lower incisors of D. isaloi are very similar to the holotype teeth of Tecovasaurus murryi and the fourth upper incisor of D. isaloi has a similar morphology to Lucianosaurus wildi. Thus the characters that have been used to diagnose at least several of these 'tooth taxa' converge on other forms and are not autapomorphic. Although it would be tempting to use the teeth of Tecovasaurus and Lucianosaurus to suggest the further presence of cynodonts in the Triassic of the American southwest, we cannot discount the similarities of these teeth to archosaurian forms as well and therefore as noted by Kammerer et al., these isolated teeth can presently only be assigned to the level of Amniota rather than Archosauriformes.
REFERENCES
Heckert, A.B. 2004. Late Triassic
microvertebrates from the lower Chinle Group (Otischalkian-Adamanian: Carnian),
southwestern U. S. A. New Mexico Museum of Natural History and Science
Bulletin 27:1-170.
Hunt, A. P., and S.G. Lucas. 1994. Ornithischian dinosaurs from the Upper
Triassic of the United States. pp. 227–241 in In the Shadows of the Dinosaurs:
Early Mesozoic Tetrapods (ed. N. C. Fraser & H.-D. Sues). Cambridge
University Press.
Irmis, R. B., Parker, W. G., Nesbitt, S. J., and J. Liu. 2007. Early ornithischian dinosaurs: the Triassic record. Historical Biology 19:3-22.
Kammerer, C. F., Flynn, J. J., Ranivoharimanana,
L., and A. R. Wyss. 2012. Ontogeny in the Malagasy traversodontid Dadadon
isaloi and a reconsideration of its phylogenetic relationships. Fieldiana
Life and Earth Sciences 5:112-125.
Parker, W.G., Irmis, R.B., Nesbitt, S.J., Martz, J.W., and L.S. Browne. 2005.
The Late Triassic pseudosuchian Revueltosaurus callenderi and its
implications for the diversity of early ornithischian dinosaurs. Proceedings of
the Royal Society B 272:963-969.
Ontogeny of the Malagasy Traversodontid Dadadon isaloi
Kammerer, C. F., Flynn, J. J., Ranivoharimanana, L., and A. R. Wyss. 2012. Ontogeny in the Malagasy Traversodontid Dadadon isaloi and a Reconsideration of its Phylogenetic Relationships. Fieldiana Life and Earth Sciences 5:112-125. doi: http://www.bioone.org/doi/abs/10.3158/2158-5520-5.1.112
Abstract - New craniodental material of the traversodontid Dadadon isaloi from Middle/Upper Triassic basal “Isalo II” beds of southwestern Madagascar is described. These specimens reveal several new autapomorphies of Dadadon, including paired foramina on the frontal near the anterior border of the postorbital and lower incisors with denticulated distal margins. The new material covers a broad size range, providing the first information on ontogeny in Dadadon. Larger (presumably older) specimens of Dadadon isaloi have more postcanine teeth, relatively longer, narrower snouts, and a higher degree of cranial ornamentation than smaller specimens. Postcanine replacement in Dadadon was similar to that of other traversodontids: new teeth erupted at the posterior end of the postcanine tooth row and moved forward. Using information from the new specimens, the position of Dadadon was tested in a new phylogenetic analysis of traversodontids. In the new analysis, Dadadon is strongly supported as a member of a clade also including the South American taxa Massetognathus and Santacruzodon, here named Massetognathinae subfam. nov. This clade is diagnosed by the presence of denticulated lower incisors, relatively small canines, three cusps in the labial margin of the upper postcanines, and low, flat skulls. Massetognathinae is the sister-group of Gomphodontosuchinae, which includes Gomphodontosuchus, Menadon, Protuberum, Exaeretodon, and Scalenodontoides. The Laurasian traversodontids (Arctotraversodon, Boreogomphodon, and Nanogomphodon) form a clade that is the sister-taxon of Massetognathinae + Gomphodontosuchinae. Denticulated incisors evolved multiple times in traversodontid evolution (in massetognathines and Arctotraversodon), and thus this group represents another possibility (besides various archosauromorphs) to be considered when attempting to identify isolated Triassic teeth with denticulated carinae lacking cingula.
Abstract - New craniodental material of the traversodontid Dadadon isaloi from Middle/Upper Triassic basal “Isalo II” beds of southwestern Madagascar is described. These specimens reveal several new autapomorphies of Dadadon, including paired foramina on the frontal near the anterior border of the postorbital and lower incisors with denticulated distal margins. The new material covers a broad size range, providing the first information on ontogeny in Dadadon. Larger (presumably older) specimens of Dadadon isaloi have more postcanine teeth, relatively longer, narrower snouts, and a higher degree of cranial ornamentation than smaller specimens. Postcanine replacement in Dadadon was similar to that of other traversodontids: new teeth erupted at the posterior end of the postcanine tooth row and moved forward. Using information from the new specimens, the position of Dadadon was tested in a new phylogenetic analysis of traversodontids. In the new analysis, Dadadon is strongly supported as a member of a clade also including the South American taxa Massetognathus and Santacruzodon, here named Massetognathinae subfam. nov. This clade is diagnosed by the presence of denticulated lower incisors, relatively small canines, three cusps in the labial margin of the upper postcanines, and low, flat skulls. Massetognathinae is the sister-group of Gomphodontosuchinae, which includes Gomphodontosuchus, Menadon, Protuberum, Exaeretodon, and Scalenodontoides. The Laurasian traversodontids (Arctotraversodon, Boreogomphodon, and Nanogomphodon) form a clade that is the sister-taxon of Massetognathinae + Gomphodontosuchinae. Denticulated incisors evolved multiple times in traversodontid evolution (in massetognathines and Arctotraversodon), and thus this group represents another possibility (besides various archosauromorphs) to be considered when attempting to identify isolated Triassic teeth with denticulated carinae lacking cingula.
Biomechanical Analysis of Triassic Cynodonts from Madagascar
Ranivoharimanana, L. 2012. Analyse biomécanique masticatrice chez des traversodontidés eucynodontes du Trias de Madagascar. [Biomechanical analysis of the jaw apparatus in eucynodont traversodontids from the Triassic of Madagascar]. Geodiversitas 34: 505–515.
Abstract - Mandible biomechanics analysis cannot take place without the understanding of the development degree and the arrangement pattern of the adductor muscles. In the non mammalian cynodonts, the temporal and the superficial masseter muscles play a primordial role in the lower jaw motion during the food processing. They constitute the key elements of this analysis. Previous studies on non mammalian cynodonts including Dadadon isaloi Flynn, Parrish, Rakotosamimanana, Simpson & Wyss, 1999 and Menadon besairiei Flynn, Parrish, Rakotosamimanana, Simpson & Wyss, 1999 demonstrated the realization, by these animals, of a complex dynamic occlusion of the lower and superior postcanine teeth. The consideration of the bite point as second occlusal fulcrum equal in status to the cranio-mandibular joint is the basis of the bifulcral model. This methodology allows: 1) to quantify the resistance opposed by food at the level of the occlusal site; and 2) to highlight a positive net vertical load, of compressive nature, acting to the level of the cranio-mandibular joint during the interactivity of the elevator muscles, i.e. during mastication.
Abstract - Mandible biomechanics analysis cannot take place without the understanding of the development degree and the arrangement pattern of the adductor muscles. In the non mammalian cynodonts, the temporal and the superficial masseter muscles play a primordial role in the lower jaw motion during the food processing. They constitute the key elements of this analysis. Previous studies on non mammalian cynodonts including Dadadon isaloi Flynn, Parrish, Rakotosamimanana, Simpson & Wyss, 1999 and Menadon besairiei Flynn, Parrish, Rakotosamimanana, Simpson & Wyss, 1999 demonstrated the realization, by these animals, of a complex dynamic occlusion of the lower and superior postcanine teeth. The consideration of the bite point as second occlusal fulcrum equal in status to the cranio-mandibular joint is the basis of the bifulcral model. This methodology allows: 1) to quantify the resistance opposed by food at the level of the occlusal site; and 2) to highlight a positive net vertical load, of compressive nature, acting to the level of the cranio-mandibular joint during the interactivity of the elevator muscles, i.e. during mastication.
RÉSUMÉ - L'analyse de la biomécanique de la mandibule ne peut s'effectuer sans la compréhension du degré de développement et du type d'arrangement des muscles adducteurs. Chez les cynodontes non mammaliens, le muscle temporal et le masséter superficiel jouent un rôle primordial dans les mouvements de la mâchoire inférieure lors de la transformation alimentaire. Ils constituent ainsi les éléments clés de cette analyse. Des études antérieures sur des cynodontes non mammaliens dont Dadadon isaloi Flynn, Parrish, Rakotosamimanana, Simpson & Wyss, 1999 et Menadon besairiei Flynn, Parrish, Rakotosamimanana, Simpson & Wyss, 1999, ont démontré la réalisation, par ces animaux, d'une occlusion dynamique complexe des dents postcanines, inférieures et supérieures. La considération du point de morsure comme second point d'appui au même titre que l'articulation crânio-mandibulaire est le fondement même du système à double leviers. Cette méthodologie a permis de: 1) quantifier la résistance opposée par la nourriture au niveau du site occlusal; et 2) mettre en évidence l'existence d'une charge verticale nette positive, de nature compressive agissant au niveau de l'articulation crânio-mandibulaire chez Dadadon isaloi et Menadon besairiei durant l'interactivité des muscles élévateurs au cours de la mastication.
Early Triassic Ichnoassemblages of Wyoming
This new paper suggests the presence of dinosauromorph (cf. Rotodactylus) and turtle-like (cf. Chelonipus) trackmakers from the Lower Triassic of Wyoming.
Lovelace, D. M., and S. D. Lovelace. 2012. Paleoenvironments and paleoecology of a Lower Triassic invertebrate and vertebrate ichnoassemblage from the Red Peak Formation (Chugwater Group), central Wyoming. Palaios 27:636-657. doi: 10.2110/palo.2012.p12-011r
Abstract - The Lower Triassic Red Peak Formation of the Chugwater Group has long been considered to have an extremely poor paleontological record, although the cause for the apparent dearth of fossils has yet to be been determined. During the course of fieldwork in central Wyoming numerous vertebrate and invertebrate ichnogenera (n ≥ 11) were observed. Vertebrate tracks and trackways representative of dinosauromorph, archosaur, lepidosaur, and testudinate trackmakers were found (cf. Rotodactylus, Chirotherium barthii, Rhynchosauroides, and cf. Chelonipus respectively). An invertebrate ichnoassemblage composed of at least 6 ichnogenera consistent with the Scoyenia ichnofacies were also found (e.g., Diplichnites, Lockeia, Fuersichnus communis, Palaeophycus striatus, cf. Scoyenia, and cf. Scolicia). The majority of these tracks and traces were found in the upper platy facies (upper 10–20 m of the Red Peak Formation), which is thought to be no younger than upper Spathian in age. Sedimentary structures, architectural elements, and lateral stratigraphic relationships support the interpretation of floodplain, fluvial, and lacustrine deposition for the upper platy facies in central Wyoming. The Red Peak Formation vertebrate and invertebrate ichnoassemblages, along with their associated depositional environments, are consistent with a fluviolacustrine (continental) setting comparable to those described from Lower to Middle Triassic strata with a Pangean distribution, including the Moenkopi Formation in the southwestern United States. This ichnoassemblage provides the first opportunity to observe paleoecological diversity and associated paleoenvironments within the Lower Triassic of the Chugwater Group.
Lovelace, D. M., and S. D. Lovelace. 2012. Paleoenvironments and paleoecology of a Lower Triassic invertebrate and vertebrate ichnoassemblage from the Red Peak Formation (Chugwater Group), central Wyoming. Palaios 27:636-657. doi: 10.2110/palo.2012.p12-011r
Abstract - The Lower Triassic Red Peak Formation of the Chugwater Group has long been considered to have an extremely poor paleontological record, although the cause for the apparent dearth of fossils has yet to be been determined. During the course of fieldwork in central Wyoming numerous vertebrate and invertebrate ichnogenera (n ≥ 11) were observed. Vertebrate tracks and trackways representative of dinosauromorph, archosaur, lepidosaur, and testudinate trackmakers were found (cf. Rotodactylus, Chirotherium barthii, Rhynchosauroides, and cf. Chelonipus respectively). An invertebrate ichnoassemblage composed of at least 6 ichnogenera consistent with the Scoyenia ichnofacies were also found (e.g., Diplichnites, Lockeia, Fuersichnus communis, Palaeophycus striatus, cf. Scoyenia, and cf. Scolicia). The majority of these tracks and traces were found in the upper platy facies (upper 10–20 m of the Red Peak Formation), which is thought to be no younger than upper Spathian in age. Sedimentary structures, architectural elements, and lateral stratigraphic relationships support the interpretation of floodplain, fluvial, and lacustrine deposition for the upper platy facies in central Wyoming. The Red Peak Formation vertebrate and invertebrate ichnoassemblages, along with their associated depositional environments, are consistent with a fluviolacustrine (continental) setting comparable to those described from Lower to Middle Triassic strata with a Pangean distribution, including the Moenkopi Formation in the southwestern United States. This ichnoassemblage provides the first opportunity to observe paleoecological diversity and associated paleoenvironments within the Lower Triassic of the Chugwater Group.
New Triassic Animal Video Clips (Museum in a Minute) from the New Mexico Museum of Natural History and Science
The New Mexico Museum of Natural History and Science has released a bunch of short, one minute video clips on a variety of fossil animals. I've linked a few of the Triassic-themed ones below. I think this is a great idea.
Revueltosaurus
Coelophysis
What is a Metoposaur?
Revueltosaurus
Coelophysis
What is a Metoposaur?
Numerous Triassic Presentation Abstracts from the Fourth Latinamerican Congress of Vertebrate Paleontology
A new issue of the South American journal Ameghiniana includes (starting on page 32) the set of published abstracts from the IV Congreso Latinamericano de Paleontologia Vertebrados, which was held in San Juan Argentina in September of 2011. There are numerous Triassic themed abstracts in here as there were sessions of basal archosaurs, early theropods, therapsids, as well as geological sessions. I gave two talks at the meeting, one on newly discovered cranial material of Poposaurus gracilis; the other on the stratigraphic position of the Placerias Quarry of Arizona, which contains the earliest known neotheropod dinosaur. A volume is currently in press containing many of the papers from the basl archosaurs session.
You can download the published abstract volume here:
http://www.ameghiniana.org.ar/index.php/ameghiniana
Once the page loads, click on the small text "PDF" in the lower right corner.
You can download the published abstract volume here:
http://www.ameghiniana.org.ar/index.php/ameghiniana
Once the page loads, click on the small text "PDF" in the lower right corner.
Footprints of Large Theropod Dinosaurs from the Late Triassic of Brazil
The Caturrita Formation may be younger than previously thought and there is a currently undiscovered large theropod in the latest Triassic of Brazil.
da Silva, R. C., Barboni, R., Dutra, T., Godoy, M. M., and R. B. Binotto. 2012. Footprints of large theropod dinosaurs and implications on the age of Triassic biotas from southern Brazil. Journal of South American Earth Sciences 39:16-23. http://dx.doi.org/10.1016/j.jsames.2012.06.017
Abstract - Dinosaur footprints found in an outcrop of the Caturrita Formation (Rio Grande do Sul State, Southern Brazil), associated with a diverse and well preserved record of fauna and flora, reopen the debate about its exclusive Triassic age. The studied footprints were identified as Eubrontes isp. and are interpreted as having been produced by large theropod dinosaurs. The morphological characteristics and dimensions of the footprints are more derived than those commonly found in the Carnian–Norian, and are more consistent with those found during the Rhaetian–Jurassic. The trackmaker does not correspond to any type of dinosaur yet known from Triassic rocks of Brazil. Recent studies with the paleofloristic content of this unit also support a more advanced Rhaetian or even Jurassic age for this unit.
da Silva, R. C., Barboni, R., Dutra, T., Godoy, M. M., and R. B. Binotto. 2012. Footprints of large theropod dinosaurs and implications on the age of Triassic biotas from southern Brazil. Journal of South American Earth Sciences 39:16-23. http://dx.doi.org/10.1016/j.jsames.2012.06.017
Abstract - Dinosaur footprints found in an outcrop of the Caturrita Formation (Rio Grande do Sul State, Southern Brazil), associated with a diverse and well preserved record of fauna and flora, reopen the debate about its exclusive Triassic age. The studied footprints were identified as Eubrontes isp. and are interpreted as having been produced by large theropod dinosaurs. The morphological characteristics and dimensions of the footprints are more derived than those commonly found in the Carnian–Norian, and are more consistent with those found during the Rhaetian–Jurassic. The trackmaker does not correspond to any type of dinosaur yet known from Triassic rocks of Brazil. Recent studies with the paleofloristic content of this unit also support a more advanced Rhaetian or even Jurassic age for this unit.
A New Ctenosauriscid from Eastern Europe, Bystrowisuchus flerovi May Represent the Oldest Known Crown-Group Archosaur
This paper describes a new ctenosauriscid archosaur from the Early Triassic of Europe. Bystrowisuchus flerovi is based upon a series of fragmentary cervical vertebrae and a partial right ilium. It differs from other ctenosauriscids in the presence of expanded spine tables on the apices of the neural spines, and by possessing generally shorter neural spines. Based on these characters Sennikov considers Bystrowisuchus to be transitional between rauisuchids and ctenosauriscids. Note that Sennikov prefers to use traditional Linnaean systematics rather than cladistics (and still recognizes Thecodontia as a taxonomic entity). A new family Lotosauridae is erected and considered distinct from other ctenosauriscids [Ctenosauriscidae]. The type locality is dated latest Olenekian, which means that Bystrowisuchus is probably older than Xilousuchus which is ambiguously from the latest Olenekian-early Anisian of China and therefore could represent the oldest record of a ctenosauriscid and crown-group archosaur.
Sennikov, A. G. 2012. The first ctenosauriscid (Reptilia: Archosauromorpha) from the Lower Triassic of Eastern Europe. Paleontological Journal [Paleontologicheskii Zhurnal] 46:499-511.
Abstract - A new Early Triassic thecodont from the Donskaya Luka locality is described. A new species and genus of Rauisuchidae, Bystrowisuchus flerovi gen. et sp. nov., the first East European and earliest known member of the family Ctenosauriscidae is established. The taxonomy and phylogeny of Rauisuchidae and their stratigraphical and geographical distribution in connection with new finds are discussed.
A New Turtle Dominated Fossil Biota from the Late Triassic (Norian) of Poland
This paper documents a newly discovered fauna from the Norian of Poland that is important because it is dominated by fossils of what is most likely a new taxon of turtle. Of course Late Triassic terrestrial turtles are very rare so we will watch further research from this site with interest. The locality also includes other vertebrate taxa including a coelophysoid dinosaur and an aetosaur. The aetosaur is of interest because the dorsal vertebra possesses a distinct hyposphene, a character previously only found in Desmatosuchus from North America and Aetobarbakinoides from Brazil. This new site is also significant because it preserves micro and macrofloral fossils, which are generally uncommonly associated with vertebrate remains. Large temnospondyls are also rare in the Norian, but this site has one as well.
Sulej, T., Niedźwiedzki, G., and R. Bronowicz. 2012. A new Late Triassic vertebrate fauna from Poland with turtles, aetosaurs, and coelophysoid dinosaurs. Journal of Vertebrate Paleontology 23: 1033-1041. DOI:10.1080/02724634.2012.694384
Abstract - We report a new site with an occurrence of isolated bones of a Palaeochersis-like turtle in Norian-Rhaetian fluvial sediments from southern Poland. The turtle remains are associated with bones of a medium-sized aetosaur, a coelophysoid dinosaur, and a larger carnivorous archosaur, as well as a hybodontid shark, ganoid and dipnoan fishes, and a large temnospondyl.
You Don't Need to Purchase Articles for Outrageous Fees Anymore. You Can Now RENT Them Instead!
In putting together my last post I noticed something interesting (disturbing?) from the Cambridge Journals site. If you would like to purchase a PDF of the Parringtonia gracilis redescription paper I just mentioned it will cost you $45.00 U.S. The atrociousness of this has been discussed in detail at several other blogs most notably by the SV-POW guys. Anyhow, for those of you who don't want to (or can't afford to) shell out this kind of cash for a single article there is now another option available. You can rent the article instead for the low(er) price of $5.99 U.S.!!! You get 24 hour access to the article, which is probably enough to cram in a couple of readings if you don't really want to fully comprehend the paper. Also just think of the hard drive space you'll save if all of your PDFs 'disappeared' after a 24 hour period. Currently I'm very hard pressed to think of a reason why this would be attractive. I suppose if you simply wanted to download the article and print it for future use.... Anyone else able to present this in a positive light?
Redescription of the Archosaur Parringtonia gracilis from the Middle Triassic Manda Beds of Tanzania
Here is another redescription of another of the enigmatic archosauriforms from the Middle Triassic Manda Formation. This study confirms the affinity of Parringtonia gracilis and Erpetosuchus granti, and reinforces the importance of redescribing these older taxa using an apomorphy-based approach and placing them in a modern phylogenetic analysis. Unfortunately the exact position of Erpetosuchidae with Archosauria was not able to be precisely determined.
Nesbitt, S. J., and R. J. Butler. 2012. Redescription of the archosaur Parringtonia gracilis from the Middle Triassic Manda beds of Tanzania, and the antiquity of Erpetosuchidae. Geological Magazine (FirstView article), 14p. doi:10.1017/S0016756812000362
Abstract - Parringtonia gracilis Huene, 1939 is represented by both cranial and postcranial material collected from the lower Middle Triassic (Anisian) Lifua Member of the Manda beds in southwestern Tanzania. This aberrant taxon was previously proposed to have affinities with pseudosuchian archosaurs, and specifically with the enigmatic Erpetosuchus granti from the Upper Triassic of Scotland. Here, we confirm the close affinities of Parringtonia gracilis and Erpetosuchus granti based on the following unambiguous synapomorphies: mediolaterally expanded posterior portion of the maxilla, alveoli present only in the anterior half of the maxilla, and absence of tooth serrations. Furthermore, the two taxa share osteoderms with deep sculpturing, a deep fossa on the dorsal margin of the neural spines and a heavily waisted shaft of the scapula. We added both Parringtonia gracilis and Erpetosuchus granti into a comprehensive phylogenetic analysis of early archosaurs and found that these taxa are clearly referable to Archosauria but that relationships are poorly resolved at the base of this clade. However, our analysis demonstrates that Erpetosuchus granti is not closely related to Crocodylomorpha, as has been hypothesized previously. The Erpetosuchidae are a clade of small-bodied archosaurs that have a poor fossil record but have members from both northern and southern Pangaea, ranging temporally from the Middle to Late Triassic. Thus, Erpetosuchidae is part of the early archosaurian radiation.
Diandongosuchus, A New Archosaur from Triassic of China
There are lots of incredible specimens coming out of the Middle Triassic in recent years (SVP attendees will see another in a talk this year by Sterling Nesbitt and colleagues), and this amazing fossil from the Ladinian of China does not disappoint. It consists of most of a partially articulated/associated skeleton found in marine sediments not far from where the early diverging poposauroid Qianosuchus mixtus was recovered some time ago.
The authors have provided color figures that allow the reader to see many of the details of the skeleton; however, the semi-articulated nature of the specimen seems to prelude dismantling of the specimen to see three dimensional views of the specimen. Furthermore, because it is in a marine shale, some crushing of the specimen has occurred. This is unfortunate because it does not allow clear study of the ilia or of the ends of the femora, which would provide key characters for the taxonomic placement of the specimen. Li et al. do code the specimen into Sterling Nesbitt's recent (2011) phylogenetic matrix of Archosauriformes and it is recovered, with much support, as the earliest diverging poposauroid. This is of interest of course because it suggests that the plesiomorphic conditions for poposauroids are quadrupedal, toothed, long-snouted forms that lack an expanded dorsal sail, possess osteoderms, and are possibly semi-aquatic. Compare this to other members of the clade such as Effigia okeeffae. The amount of morphological variation in this group is incredible.
I'll admit that I'm not entirely convinced of the phylogenetic placement of this specimen, but unfortunately I cannot get into the details of why at this time. Let's just say that this is an extremely interesting taxon that should be the subject of debate for a while to come. I do really wish the ilia were better preserved or more visible, but it is really hard to complain about such a beautiful fossil.
Li, C., Wu, X.-C., Zhao, L.-J., Sato, T. and L.-T. Wang. 2012. A new archosaur (Diapsida, Archosauriformes) from the marine Triassic of China. Journal of Vertebrate Paleontology 32(5): 1064-1081. DOI:10.1080/02724634.2012.694383http://www.tandfonline.com/doi/abs/10.1080/02724634.2012.694383
Abstract - A new Middle Triassic archosaur, Diandongosuchus fuyuanensis, gen. et
sp. nov., is described on the basis of a skeleton from the Zhuganpo Member (Ladinian) of the Falang Formation, eastern Yunnan Province, China. It is primarily characterized by the nasal process of the premaxilla extending posteriorly well beyond the external naris, the super-sized coracoid foramen laterally bordered by the scapula, the ischium with a strongly expanded medial portion anteroposteriorly longer than the proximodistal height of the bone, and anteriorly notched cervical osteoderms. D. fuyuanensis is a pseudosuchian on the basis of the crocodile-normal tarsal joint and other features, such as the distal end of the ulna in posterolateral view squared off, osteoderms with a distinct anterior process, the presacral vertebrae dorsally covered by more than one osteoderm, dorsal osteoderm alignment dorsal to presacrals 10–24 staggered, the pubis-ischium contact reduced to a thin proximal contact, and the medial contact of the ischia extensive but the dorsal margins separate. It is from a marine deposit but shows few morphological adaptations of the postcranial skeleton for a semiaquatic way of life when compared with Qianosuchus from the Anisian limestone of the same area. A phylogenetic analysis derived from an existing data matrix suggests that the new archosaur occupies the basal-most position in Poposauroidea and further confirms the poposauroid status of Qianosuchus. On the basis of current information, the discovery of Diandongosuchus does not firmly underscore the affinity of the semiterrestrial vertebrate faunas between the eastern and western regions along the northern coastline of the Tethys.
The authors have provided color figures that allow the reader to see many of the details of the skeleton; however, the semi-articulated nature of the specimen seems to prelude dismantling of the specimen to see three dimensional views of the specimen. Furthermore, because it is in a marine shale, some crushing of the specimen has occurred. This is unfortunate because it does not allow clear study of the ilia or of the ends of the femora, which would provide key characters for the taxonomic placement of the specimen. Li et al. do code the specimen into Sterling Nesbitt's recent (2011) phylogenetic matrix of Archosauriformes and it is recovered, with much support, as the earliest diverging poposauroid. This is of interest of course because it suggests that the plesiomorphic conditions for poposauroids are quadrupedal, toothed, long-snouted forms that lack an expanded dorsal sail, possess osteoderms, and are possibly semi-aquatic. Compare this to other members of the clade such as Effigia okeeffae. The amount of morphological variation in this group is incredible.
I'll admit that I'm not entirely convinced of the phylogenetic placement of this specimen, but unfortunately I cannot get into the details of why at this time. Let's just say that this is an extremely interesting taxon that should be the subject of debate for a while to come. I do really wish the ilia were better preserved or more visible, but it is really hard to complain about such a beautiful fossil.
Li, C., Wu, X.-C., Zhao, L.-J., Sato, T. and L.-T. Wang. 2012. A new archosaur (Diapsida, Archosauriformes) from the marine Triassic of China. Journal of Vertebrate Paleontology 32(5): 1064-1081. DOI:10.1080/02724634.2012.694383http://www.tandfonline.com/doi/abs/10.1080/02724634.2012.694383
Abstract - A new Middle Triassic archosaur, Diandongosuchus fuyuanensis, gen. et
sp. nov., is described on the basis of a skeleton from the Zhuganpo Member (Ladinian) of the Falang Formation, eastern Yunnan Province, China. It is primarily characterized by the nasal process of the premaxilla extending posteriorly well beyond the external naris, the super-sized coracoid foramen laterally bordered by the scapula, the ischium with a strongly expanded medial portion anteroposteriorly longer than the proximodistal height of the bone, and anteriorly notched cervical osteoderms. D. fuyuanensis is a pseudosuchian on the basis of the crocodile-normal tarsal joint and other features, such as the distal end of the ulna in posterolateral view squared off, osteoderms with a distinct anterior process, the presacral vertebrae dorsally covered by more than one osteoderm, dorsal osteoderm alignment dorsal to presacrals 10–24 staggered, the pubis-ischium contact reduced to a thin proximal contact, and the medial contact of the ischia extensive but the dorsal margins separate. It is from a marine deposit but shows few morphological adaptations of the postcranial skeleton for a semiaquatic way of life when compared with Qianosuchus from the Anisian limestone of the same area. A phylogenetic analysis derived from an existing data matrix suggests that the new archosaur occupies the basal-most position in Poposauroidea and further confirms the poposauroid status of Qianosuchus. On the basis of current information, the discovery of Diandongosuchus does not firmly underscore the affinity of the semiterrestrial vertebrate faunas between the eastern and western regions along the northern coastline of the Tethys.
More Photos from the Petrified Forest
I'm currently creating a database of all of our photos from the last decade of paleontological work at Petrified Forest National Park and am working through 2002. These photos were taken by Daniel Woody who was investigating the Sonsela Member of the Chinle Formmation and assisting with the paleontology work. I'm amazed how far the quality of digital photos have over the decade!
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| Phytosaur lower jaw in the Crystal Forest |
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| Phytosaur quadrate bone in the Blue Mesa Member |
Triassic Fieldwork in Utah
Randall Irmis of the Utah Museum of Natural History is posting about current fieldwork in the Triassic of Utah. You can check out the first post here and check back for more to follow.
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