Two last minute papers for 2009 from Palaeodiversity. This is an open access journal so these papers and others can be downloaded for free from here.
Maisch, M.V., Vega, C.S., and R.R. Schoch. 2009. No dicynodont in the Keuper – a reconsideration of the occurrence of aff. Dinodontosaurus in the Middle Triassic of Southern Germany. Palaeodiversity 2:271-278.
Abstract - An isolated humerus, attributed to a dicynodont therapsid and identified as aff. Dinodontosaurus, from the Lower Keuper (Middle Ladinian, Middle Triassic) of southwestern Germany is redescribed. An additional but smaller humerus that is similar in morphology might pertain to the same taxon. Several morphological features preclude an identification of the material as either aff. Dinodontosaurus, a dicynodont, or even a synapsid. The deltopectoral crest shows a number of tubercles, probably for muscle attachment. The supinator process is strongly developed and clearly offset from the rest of the bone. The distal articulation facet is very narrow transversely. There is no foramen entepicondyloideum. The ectepicondyle has a deeply concave distal surface, at least in the large and presumably adult specimen. An alternative identification for the two humeri proves difficult, as they do not agree with any other known tetrapod from the Lower Keuper. They bear close resemblance, however, to the humerus of the Permian temnospondyl Eryops, suggesting the presence of an as yet unknown temnospondyl.
This paper also emphasizes the importance of correctly determining taxonomic identity when using incomplete or unique specimens for biostratigraphic correlations.
Spielmann, J.A., Lucas, S.G., Heckert, A.B., Rinehart, L.F., and H. R. Richards III. 2009. Redescription of Spinosuchus caseanus (Archosauromorpha: Trilophosauridae) from the Upper Triassic of North America. Palaeodiversity 2: 283–313.
Abstract - Our reexamination of the holotype of Spinosuchus caseanus from the Upper Triassic of West Texas, in addition to the recognition of additional records of this taxon, demonstrates that it is closely related to the trilophosaurid archosauromorph Trilophosaurus and thus is included in a revised Trilophosauridae. Previous arguments suggesting that features that unite Spinosuchus and Trilophosaurus are not limited to these two taxa or are symplesiomorphies shared with a wide variety of contemporaneous Triassic archosauromorphs are not substantiated based on a detailed comparative analysis of the two taxa. The distinctive neural spine morphology of Spinosuchus allows for recognition of this taxon based on isolated vertebrae and thus increases its biostratigraphic value. Spinosuchus is restricted to strata of Adamanian age and is therefore an index taxon of the Adamanian land-vertebrate faunachron.
One interesting aspect of the new referred specimens of Spinosuchus is that they co-occur in a quarry in which the only other recovered material (cranial and postcranial) has been referred to Trilophosaurus jacobsi (Spielmann et al., 2007). Dorsal and sacral vertebrae from the quarry represent Spinosuchus, whereas all of the other material (that does not include dorsal and sacral vertebrae) where referred to T. jacobsi (i.e. there is no duplication of elements). Thus, although discounted by Spielmann et al. (2009) is seems possible that all of the material may indeed belong to a single taxon and that T. jacobsi would be a junior synonym of S. caseanus. Spielmann et al. (2009) claim that dorsal vertebrae from the quarry exist that are more similar to Trilophosaurus buettneri and not Spinosuchus, thus the taxa are not the same, but this will have to await future description of this material.
It also seems strange (and unstable) to diagnose Trilophosauridae based solely on shared vertebral laminae and not including characters of the unique skull and tooth morphology that has historically diagnosed the taxon, but again this determination will rely on future material being recovered.
Tawa hallae makes USA Today's List of "Biggest Discoveries in Science" for 2009
http://www.usatoday.com/tech/science/2009-12-29-science2009review29_ST_N.htm?loc=interstitialskip
Good to see paleontology and the anniversary of Charles Darwin's birth figured prominently.
Good to see paleontology and the anniversary of Charles Darwin's birth figured prominently.
End of the Year Happenings
I have not posted for a bit, things have been quite slow in the Triassic recently and I've been busy with the holidays. I also just joined Facebook and am trying to figure out what it is all about, however, most of my recent effort has been going towards finishing up (and starting) a group of manuscripts that are either due or that I have been wanting to get to for a long time.
I'm working on a few year end posts, which I hope to have out soon, but in the meantime I've been engrossed in Scott Sampson's recent book "Dinosaur Odyssey" (a Christmas present). I don't normally read too many general dinosaur books, usually preferring paleontologist biographies, books on historic field work, or civil war histories, but Scott's book is highly interesting and informative and I'm having a hard time putting it down. I'm only a third of the way through, but would already highly recommend it as a good current read on dinosaur paleontology. I'm also deeply honored that Scott mentions our recent Triassic work, especially on early dinosaurs.
I'm working on a few year end posts, which I hope to have out soon, but in the meantime I've been engrossed in Scott Sampson's recent book "Dinosaur Odyssey" (a Christmas present). I don't normally read too many general dinosaur books, usually preferring paleontologist biographies, books on historic field work, or civil war histories, but Scott's book is highly interesting and informative and I'm having a hard time putting it down. I'm only a third of the way through, but would already highly recommend it as a good current read on dinosaur paleontology. I'm also deeply honored that Scott mentions our recent Triassic work, especially on early dinosaurs.
Another Mystery Fossil from the Chinle
The identification of these two specimens has been bugging me for a few years now. These are the only two specimens like this that I have ever seen and they were collected from pretty much the same locality and horizon (Sonsela Member, Chinle Formation) in the Petrified Forest. They are thick bones, characterized by their triangular shape (one is missing a corner) and by a short but deep notch in what presumably is the dorsal end. It is bilaterally symmetrical, thus represents a mid-line element, and the lateral edges show possible open sutures. The photos show the tops and updersides of the two elements.
I have a working hypothesis on what I think they are (at least what bone) but I'd like to hear your opinions.
I have a working hypothesis on what I think they are (at least what bone) but I'd like to hear your opinions.I Swear I Didn't Say That! Having someone else put your foot in your mouth for you
One of the scariest things I've found about being contacted by the media regarding your scientific expertise on a particular subject is reading or hearing the end results. Quite often due to either a lack of comprehension on the part of the interviewer or some final editing what appears is not quite what you meant (or in some cases the complete opposite). It is not so easy to shrug this off in the days of "You Tube" and file sharing as this is now a permanent (and often heavily distributed) record of you saying something that you did not, especially if you do not agree with what "you said" at all. Possibly this could be embarrassing for you as well depending on how your "thoughts" are perceived by your colleagues.
Matt Wedel was the recent recipient of this type of "quote mining" as Darren Naish put it (including having his name mispelled through the entire show). He is quite angry about it and has commented here and here. Several fellow bloggers and colleagues have chimed in as well including Darren Naish and David Hone.
I discussed something similar on this blog a little over a year ago. In my situation I submitted proof corrections that were either not made or incorrectly made. Again this is a situation where something permanent is going on the record with my name on it containing errors that are distorting the information that I wished to provide.
Who 'proofs' the proofs, and who has the final say on scripted interviews? Because our names (and hence reputations) are on the line here, I think that it should be us, the scientists. I think that it is simply common courtesy to check back during final production and make sure that we are being accurately represented, as often we are providing this information also as a courtesy. Maybe it is simply best just not to answer the phone, but really that is against all we stand for as scientists. Science is meant to be shared and discussed and tested; however, it's often pretty rough to have to defend yourself for something someone else actually said.
By the way this also happens in exhibits and interpretive media for museums, National Parks, etc... As the specialist you really have to make sure you are involved in every step of production or you probably are not going to be happy with the end result. The question now is, what collectively as a group we can do about this to make sure it doesn't keep happening (there is actually some detailed discussion of such options going on right now on the various vertebrate paleontology list servers)? How do you get yourself involved in on the final production when simple common courtesy isn't happening?
Matt Wedel was the recent recipient of this type of "quote mining" as Darren Naish put it (including having his name mispelled through the entire show). He is quite angry about it and has commented here and here. Several fellow bloggers and colleagues have chimed in as well including Darren Naish and David Hone.
I discussed something similar on this blog a little over a year ago. In my situation I submitted proof corrections that were either not made or incorrectly made. Again this is a situation where something permanent is going on the record with my name on it containing errors that are distorting the information that I wished to provide.
Who 'proofs' the proofs, and who has the final say on scripted interviews? Because our names (and hence reputations) are on the line here, I think that it should be us, the scientists. I think that it is simply common courtesy to check back during final production and make sure that we are being accurately represented, as often we are providing this information also as a courtesy. Maybe it is simply best just not to answer the phone, but really that is against all we stand for as scientists. Science is meant to be shared and discussed and tested; however, it's often pretty rough to have to defend yourself for something someone else actually said.
By the way this also happens in exhibits and interpretive media for museums, National Parks, etc... As the specialist you really have to make sure you are involved in every step of production or you probably are not going to be happy with the end result. The question now is, what collectively as a group we can do about this to make sure it doesn't keep happening (there is actually some detailed discussion of such options going on right now on the various vertebrate paleontology list servers)? How do you get yourself involved in on the final production when simple common courtesy isn't happening?
Triassic Bonanza in the New Issue of the Journal of Vertebrate Paleontology
Quite a few new Triassic papers in the December issue of JVP and one Early Jurassic paper.
Middle Triassic -
Butler, R. J., Barrett, P. M., Abel, R. L., and D. J. Gower. 2009. A possible ctenosauriscid archosaur from the Middle Triassic Manda beds of Tanzania. Journal of Vertebrate Paleontology 29:1022–1031. doi: 10.1671/039.029.0404
ABSTRACT—The Lifua Member of the Manda Beds of Tanzania (Middle Triassic: ?latest Anisian) has yielded an exceptionally important assemblage of early archosaurs, including numerous well-preserved specimens. However, the majority of this material has not been described formally, frustrating attempts to incorporate it into studies on early archosaur diversity and evolution. We describe an anterior dorsal vertebra from the Lifua Member as the holotype of a new taxon, Hypselorhachis mirabilis. Hypselorhachis is characterised by the possession of an elongate neural spine that is at least 5.5 times the height of the centrum, and can be diagnosed on the basis of a single autapomorphy relating to the morphology of the prezygapophysis. Hypselorhachis is similar to other early Middle Triassic archosaurs with elongate neural spines, including Arizonasaurus, Ctenosauriscus, and Lotosaurus. It is possible that these taxa form a clade, Ctenosauriscidae, but further anatomical and phylogenetic work is required before this can be confirmed.
-After more than 50 years of being a nomen nudum and still cited in numerous papers, Hypselorhachis is finally a diagnosed valid taxon. Now we need to find more of this animal than just a single vertebra.
Botella, H., Plasencia, P., Marquez-Aliaga, A., Cuny, G., and M. Dorka. 2009. Pseudodalatias henarejensis nov. sp. a new pseudodalatiid (Elasmobranchii) from the Middle Triassic of Spain. Journal of Vertebrate Paleontology 29:1006–1012. doi: 10.1671/039.029.0425
ABSTRACT—Pseudodalatiids, a chondrichthyan family of uncertain phylogenetic affinities, have been hitherto exclusively known from the tooth-based species Pseudodalatias barnstonensis (Sykes, 1971), which has a stratigraphic range restricted to the Upper Triassic of Europe. Pseudodalatias presents a characteristic dentition which allows it to hold and cut its prey, showing a neoselachian design, but lacking the triple-layered enameloid microstructure of neoselachian teeth. The discovery of Pseudodalatias henarejensis nov. sp. in the Ladinian of Spain extends the stratigraphical range and the palaeogeographical distribution of this family. This new species also demonstrates that a cutting-clutching dentition evolved progressively in the family Pseudodalatidiidae. Pseudodalatiids are likely to represent stem-batoids or stemneoselachians rather than aberrant hybodonts.
Kemp, T. S. 2009. The endocranial cavity of a nonmammalian eucynodont, Chiniquodon theotenicus, and its implications for the origin of the mammalian brain. Journal of Vertebrate Paleontology 29:1188–1198. doi: 10.1671/039.029.0430
ABSTRACT—The braincase and endocranial cavity of a specimen of a nonmammalian eucynodont Chiniquodon is described and illustrated, and a tentative reconstruction of the gross anatomy of the brain offered. Salient features are the well-developed impression for the olfactory lobes, the extreme narrowness of the region available for the telencephalon, and the evidence for a large cerebellum. A two-step theory for the origin of the mammalian brain is proposed. The first step is represented by the nonmammalian cynodont level and consisted of enlargement of the cerebellum and possibly midbrain structures. This stage is associated with the evolution of more sophisticated neuromuscular control of the mandibular and locomotory apparatuses. The second step was the evolution of the mammalian six-layered neocortex, and did not occur until the origin of the mammals themselves. This stage was an integral part of a complex set of allometric changes associated with miniaturization. The origin of the neocortex was correlated with sensitivity to higher frequency sound, and a greater area of olfactory epithelium, both expected to result from miniaturization, and also with the availability of increased space within the cranial cavity expected as the adductor jaw musculature was relatively reduced in mass. Overall, neocortical function was associated with the high energy nocturnal foraging activity generally believed to have appertained in the first mammals, and also sophisticated social communication.
Desojo, J. B., and A. B. Arcucci. 2009. New material of Luperosuchus fractus (Archosauria: Crurotarsi) from the Middle Triassic of Argentina: The earliest known South American 'rauisuchian'. Journal of Vertebrate Paleontology 29:1311–1315. doi: 10.1671/039.029.0422
-No abstract. This short communication redescribes the holotype and referred material of Luperosuchus and provides a modern diagnosis of the taxa. As stated by the authors rproviding modern dianoses and descriptions of material historically assigned to the 'Rauisuchia' is the first step leading to a detailed phylogenetic analysis of this group as most recent workers have hypothesized that it is paraphyletic in regards to the position of crocodylomorphs.
Lower Jurassic-
Barrett, P. M. 2009. A new basal sauropodomorph dinosaur from the Upper Elliot Formation (Lower Jurassic) of South Africa. Journal of Vertebrate Paleontology 29:1032–1045. doi: 10.1671/039.029.0401
ABSTRACT—A new basal sauropodomorph dinosaur, Massospondylus kaalae sp. nov., is named on the basis of a partial skull from the upper Elliot Formation (Lower Jurassic) of the Herschel District, South Africa. It can be distinguished from Massospondylus carinatus by a combination of character states relating to the proportions of the premaxilla, the presence of a strong ridge on the dorsolateral surface of the lacrimal, and the morphology of the braincase. The description of Massospondylus kaalae further increases sauropodomorph diversity in the previously depauperate upper Elliot fauna.
-one thing that caught my attention regarding this new taxon is that the species name honors a collection manager, a usually unheralded group when it comes to having taxa named after them. What a great honor and demonstration of the appreciation all researchers should have for the people who handle paleontological collections on a day to day basis.
Middle Triassic -
Butler, R. J., Barrett, P. M., Abel, R. L., and D. J. Gower. 2009. A possible ctenosauriscid archosaur from the Middle Triassic Manda beds of Tanzania. Journal of Vertebrate Paleontology 29:1022–1031. doi: 10.1671/039.029.0404
ABSTRACT—The Lifua Member of the Manda Beds of Tanzania (Middle Triassic: ?latest Anisian) has yielded an exceptionally important assemblage of early archosaurs, including numerous well-preserved specimens. However, the majority of this material has not been described formally, frustrating attempts to incorporate it into studies on early archosaur diversity and evolution. We describe an anterior dorsal vertebra from the Lifua Member as the holotype of a new taxon, Hypselorhachis mirabilis. Hypselorhachis is characterised by the possession of an elongate neural spine that is at least 5.5 times the height of the centrum, and can be diagnosed on the basis of a single autapomorphy relating to the morphology of the prezygapophysis. Hypselorhachis is similar to other early Middle Triassic archosaurs with elongate neural spines, including Arizonasaurus, Ctenosauriscus, and Lotosaurus. It is possible that these taxa form a clade, Ctenosauriscidae, but further anatomical and phylogenetic work is required before this can be confirmed.
-After more than 50 years of being a nomen nudum and still cited in numerous papers, Hypselorhachis is finally a diagnosed valid taxon. Now we need to find more of this animal than just a single vertebra.
Botella, H., Plasencia, P., Marquez-Aliaga, A., Cuny, G., and M. Dorka. 2009. Pseudodalatias henarejensis nov. sp. a new pseudodalatiid (Elasmobranchii) from the Middle Triassic of Spain. Journal of Vertebrate Paleontology 29:1006–1012. doi: 10.1671/039.029.0425
ABSTRACT—Pseudodalatiids, a chondrichthyan family of uncertain phylogenetic affinities, have been hitherto exclusively known from the tooth-based species Pseudodalatias barnstonensis (Sykes, 1971), which has a stratigraphic range restricted to the Upper Triassic of Europe. Pseudodalatias presents a characteristic dentition which allows it to hold and cut its prey, showing a neoselachian design, but lacking the triple-layered enameloid microstructure of neoselachian teeth. The discovery of Pseudodalatias henarejensis nov. sp. in the Ladinian of Spain extends the stratigraphical range and the palaeogeographical distribution of this family. This new species also demonstrates that a cutting-clutching dentition evolved progressively in the family Pseudodalatidiidae. Pseudodalatiids are likely to represent stem-batoids or stemneoselachians rather than aberrant hybodonts.
Kemp, T. S. 2009. The endocranial cavity of a nonmammalian eucynodont, Chiniquodon theotenicus, and its implications for the origin of the mammalian brain. Journal of Vertebrate Paleontology 29:1188–1198. doi: 10.1671/039.029.0430
ABSTRACT—The braincase and endocranial cavity of a specimen of a nonmammalian eucynodont Chiniquodon is described and illustrated, and a tentative reconstruction of the gross anatomy of the brain offered. Salient features are the well-developed impression for the olfactory lobes, the extreme narrowness of the region available for the telencephalon, and the evidence for a large cerebellum. A two-step theory for the origin of the mammalian brain is proposed. The first step is represented by the nonmammalian cynodont level and consisted of enlargement of the cerebellum and possibly midbrain structures. This stage is associated with the evolution of more sophisticated neuromuscular control of the mandibular and locomotory apparatuses. The second step was the evolution of the mammalian six-layered neocortex, and did not occur until the origin of the mammals themselves. This stage was an integral part of a complex set of allometric changes associated with miniaturization. The origin of the neocortex was correlated with sensitivity to higher frequency sound, and a greater area of olfactory epithelium, both expected to result from miniaturization, and also with the availability of increased space within the cranial cavity expected as the adductor jaw musculature was relatively reduced in mass. Overall, neocortical function was associated with the high energy nocturnal foraging activity generally believed to have appertained in the first mammals, and also sophisticated social communication.
Desojo, J. B., and A. B. Arcucci. 2009. New material of Luperosuchus fractus (Archosauria: Crurotarsi) from the Middle Triassic of Argentina: The earliest known South American 'rauisuchian'. Journal of Vertebrate Paleontology 29:1311–1315. doi: 10.1671/039.029.0422
-No abstract. This short communication redescribes the holotype and referred material of Luperosuchus and provides a modern diagnosis of the taxa. As stated by the authors rproviding modern dianoses and descriptions of material historically assigned to the 'Rauisuchia' is the first step leading to a detailed phylogenetic analysis of this group as most recent workers have hypothesized that it is paraphyletic in regards to the position of crocodylomorphs.
Lower Jurassic-
Barrett, P. M. 2009. A new basal sauropodomorph dinosaur from the Upper Elliot Formation (Lower Jurassic) of South Africa. Journal of Vertebrate Paleontology 29:1032–1045. doi: 10.1671/039.029.0401
ABSTRACT—A new basal sauropodomorph dinosaur, Massospondylus kaalae sp. nov., is named on the basis of a partial skull from the upper Elliot Formation (Lower Jurassic) of the Herschel District, South Africa. It can be distinguished from Massospondylus carinatus by a combination of character states relating to the proportions of the premaxilla, the presence of a strong ridge on the dorsolateral surface of the lacrimal, and the morphology of the braincase. The description of Massospondylus kaalae further increases sauropodomorph diversity in the previously depauperate upper Elliot fauna.
-one thing that caught my attention regarding this new taxon is that the species name honors a collection manager, a usually unheralded group when it comes to having taxa named after them. What a great honor and demonstration of the appreciation all researchers should have for the people who handle paleontological collections on a day to day basis.
Phytosaurs as the Likely Trackmaker for Apatopus from the Late Triassic of North America
Padian, K., Li, C., and J. Pchelnikova. 2009. The trackmaker of Apatopus (Late Triassic: North America): implications for the evolution of archosaur stance and gait. Palaeontology (early view). doi: 10.1111/j.1475-4983.2009.00924.x
Abstract - For some decades, a major focus of research has been on how locomotor modes changed in some archosaurian reptiles from a more or less ‘sprawling’ to an ‘erect’ posture, whether there were discrete intermediate stages, and how many times ‘erect’ posture evolved. The classic paradigm for the evolution of stance and gait in archosaurs, a three-stage transition from sprawling to ‘semi-erect’ to erect posture, has been replaced by a subtler understanding of a continuum of changing limb joint angles. We suggest a further separation of terminology related to stance vs. gait so as not to entail different processes: ‘sprawling’ and ‘erect’ should refer to continua of stance; ‘rotatory’ and ‘parasagittal’ are more appropriate ends of a continuum that describes the motions of gait. We show that the Triassic trackway Apatopus best fits the anatomy and proportions of phytosaurs, based on a new reconstruction of their foot skeleton; it is less likely to have been made by another pseudosuchian or nonarchosaurian archosauromorph. Moreover, the trackmaker was performing the high walk. A phytosaurian trackmaker would imply that the common ancestor of pseudosuchians, and therefore archosaurs could approximate the high walk (depending on phylogeny), and if so, erect stance and parasagittal gait did not evolve independently in pseudosuchians and ornithosuchians, although the kinematic mechanisms differed in the two groups. It remains to be seen how far outside Archosauria, if at all, more or less erect posture and parasagittal gait may have evolved.
Abstract - For some decades, a major focus of research has been on how locomotor modes changed in some archosaurian reptiles from a more or less ‘sprawling’ to an ‘erect’ posture, whether there were discrete intermediate stages, and how many times ‘erect’ posture evolved. The classic paradigm for the evolution of stance and gait in archosaurs, a three-stage transition from sprawling to ‘semi-erect’ to erect posture, has been replaced by a subtler understanding of a continuum of changing limb joint angles. We suggest a further separation of terminology related to stance vs. gait so as not to entail different processes: ‘sprawling’ and ‘erect’ should refer to continua of stance; ‘rotatory’ and ‘parasagittal’ are more appropriate ends of a continuum that describes the motions of gait. We show that the Triassic trackway Apatopus best fits the anatomy and proportions of phytosaurs, based on a new reconstruction of their foot skeleton; it is less likely to have been made by another pseudosuchian or nonarchosaurian archosauromorph. Moreover, the trackmaker was performing the high walk. A phytosaurian trackmaker would imply that the common ancestor of pseudosuchians, and therefore archosaurs could approximate the high walk (depending on phylogeny), and if so, erect stance and parasagittal gait did not evolve independently in pseudosuchians and ornithosuchians, although the kinematic mechanisms differed in the two groups. It remains to be seen how far outside Archosauria, if at all, more or less erect posture and parasagittal gait may have evolved.
A New Late Triassic Theropod, Tawa hallae, and its Implications for Early Dinosaur Evolution
A new Late Triassic basal theropod, Tawa hallae, is described by Nesbitt et al. (2009) in a new paper out today in Science. Tawa is known from two relatively complete skeletons and other isolated material from the Hayden Quarry at Ghost Ranch New Mexico [another link]. The Hayden Quarry is in the Petrified Forest Member of the Chinle Formation.
This quarry is an absolutely spectacular site that is proving to be the most diverse locality in the Chinle Formation, even more than the famed Coelophysis Quarry (which is close geographically but higher stratigraphically). Other taxa found at this site include Dromomeron romeri, Chindesaurus bryansmalli, Eucoelophysis baldwini, a coelophysoid theropod, and a shuvosaurid as well as various aetosaurs, crocodylomorphs, rauisuchians, phytosaurs, drepanosaurs, metoposaurs, and fish (Irmis et al. 2007).
Key points of the paper:
• Tawa possesses a mix of “coelophysoid” (Neotheropoda) and herrerasaurid characters that help clarify basal saurischian relationships.
Key points of the paper:
• Tawa possesses a mix of “coelophysoid” (Neotheropoda) and herrerasaurid characters that help clarify basal saurischian relationships.
- Herrerasaurids (Herrerasaurus, Chindesaurus, Staurikosaurus) and Eoraptor are unambiguously nested within Theropoda.
- Tawa is the sister taxon to Neotheropoda (see phylogenetic reconstruction artwork and tree below).
- Coelophysoidea is found to be paraphyletic, with the hypothesis that this clade had been serving as a “phylogenetic vacuum cleaner”, picking up deep theropod synapomorphies and ceratosaur/tetanuran reversals and treating them as coelophysoid synapomorphies.
• The presence of cervical pleurocoels in Tawa supports the hypothesis that cervical air sacs predate the origin of Neotheropoda and may be ancestral for Saurischia.
• The age of the Hayden Quarry (~215-213) and comparison with the Ischigualasto fauna supports the hypothesis of the diachronous evolution of Triassic dinosaur faunas.
• The presence of Dromomeron, Chindesaurus, Tawa, and a basal neotheropod in the Hayden Quarry suggests that the North American theropod fauna was not endemic, an was the result of several dispersals of taxa from South America.
• This prevalence of dispersal among early dinosaurs and other Triassic reptile groups indicates that physical barriers did not prevent these groups from moving around Pangaea - specifically into North America. Thus the question is why didn't sauropodomorphs and ornithischians make it to North America during the Triassic? Nesbitt et al. hypothesize that they were excluded by climate.
Dentary of Tawa hallae
Reconstruction of the head of Tawa hallae.
Articulated manus of Tawa hallae
In-situ articulated limbs of Tawa hallae
Associated dentary and maxilla of Tawa hallae
Block containing skull and other bones.
Thanks to Randy Irmis and Sterling Nesbitt for providing the photos and reconstructions used here. The reconstructions are by Jorge Gonzalez.
Links to some early news articles [here] [here] [here]
Link to National Science Foundation special report with lots of additional information on Tawa, its discovery, and its finders.
REFERENCES
Irmis, R. B, Nesbitt, S. J., Padian, K., Smith, N. D., Turner, A. H, Woody, D., and A. Downs. 2007. A Late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs. Science 317:358–361.
Nesbitt, S. J., Smith, N. D., Irmis, R. B., Turner, A. H., Downs, A., and M. A. Norell. 2009. A complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs. Science 326:1530-1533.
Paw-talk
This is an interesting site, includes a blog and also various forums ranging from everything such as wildlife conservation to pet care and grooming. Recently I was asked some questions regarding my work and blog for a blog post on this site. You can read my cheesy answers here. I also see that Matt Wedel (Ask Dr. Vector and SVPOW) also has an interview here. Brian Switek (Laelaps) also appears to be a regular contributor. Check it out.
Thanks to Ava for the invite.
Thanks to Ava for the invite.
In Memoriam Carl Gans (1923-2009)
CNAH ANNOUNCEMENT The Center for North American Herpetology Lawrence,
Kansas http://www.cnah.org 7 December 2009
IN MEMORIAM CARL GANS (1923-2009)
. . . modified from the New York Times
Dr. Carl Gans, 86, died peacefully after a long illness in Austin, Texas, on 30 November 2009. He was born in Hamburg, Germany, where he attended the Talmud Thora Realschule, and emigrated to the United States in 1939. Here he attended GeorgeWashington High School in New York City, received a Bachelor's Degree in Mechanical Engineering from New York University in 1944, a Master's Degree in Mechanical Engineering from Columbia University in 1950, a PE License from New York State in 1950, and a Doctoral Degree in Biology from Harvard in 1957. He served in the U.S. Army in the Pacific Command in the Philippines and Japan from 1944 to 1946. Carl was a John Simon Guggenheim Memorial Fellow from 1953 to 1955 conducting reptile studies in Brazil. After working eight years with Babcock & Wilcox installing power boilers, he changed careers and became a Professor of Biology and Department Chairperson at the University of Buffalo (later SUNY) from 1958 to 1971. He moved to Ann Arbor as Professor of Biology and Chairperson of Zoology at the University of Michigan until his retirement in 1998. Carl's work and hundreds of publications were in evolutionary physiology and comparative biomechanics. He carried out his primary studies in the area of reptiles and amphibians. He became world-known as editor of the journal "Morphology" for 25 years and as the editor of the monumental 23-volume "Biology of the Reptilia," published between 1969 and 2009. His first book-length publication was "Biomechanics" in which he combined his engineering and biology backgrounds. He co-authored two biology texts used in universities throughout the United States: "A Photographic Atlas of Shark Anatomy" and"Electromyography for Experimentalists." He also wrote the popular paperback book"Reptiles of the World," translated into many languages. His library of over 20,000 items in herpetology is currently at Ben Gurion University in Israel, which also has his extensive scientific correspondence. Other of his publications may be found at the Scripps Institute, University of California, San Diego, and the Museum of Comparative Zoology at Harvard. His extensive animal collections, which he gathered on five continents over many decades, can be found at the Field Museum of Natural History, Chicago, the California Academy of Sciences, San Francisco, the Carnegie Museum of Natural History, Pittsburg, and the Museum of Comparative Zoology at Harvard.
Carl was predeceased by his wife of fifty years, Mabel Kyoko Andow. He is survived by his brother Leo Gans of Teaneck, New Jersey.
*****
Memorial donations may be made to
THE CARL GANS AWARD
As some of you may be aware, we have been fund-raising for some time to endow the "Carl Gans Award," associated with the Division of Comparative Biomechanics, Society for Integrative and Comparative Biology (SICB). This award, recently approved by the SICB Executive Committee, is the first such award for the newly founded Division of Comparative Biomechanics and honors the numerous scientific and editorial contributions to biomechanics and herpetology by Carl Gans. To date, we have raised approximately two-thirds of the $25,000 required for endowment of this award. Fortunately, matching funds ($10,000) were generously made available by the late Carl Gans, his brother Leo Gans, and Sandy Gaunt that will provide a 2-for-1 match for the first $5000 contributed, no matter how small that, in conjunction with the matching offer, will let SICB takeadvantage of this new funding opportunity and enable the award to be established financially. Contributed funds should be marked for the "Carl Gans Award" and be sent to the attention of the SICB Executive Director, Brett Burk (BBurk@BurkInc.com) at the address below. He will deposit them into an account and reserve them for the fund. Send your contribution to:
Brett J. Burk SICB Executive Director 1313 Dolley Madison Boulevard, Suite 402 McLean, Virginia 22101
Contributions can also be made online at
https://ssl4.westserver.net/birenheide/secure/sicb/cart/donations.php
Kansas http://www.cnah.org 7 December 2009
IN MEMORIAM CARL GANS (1923-2009)
. . . modified from the New York Times
Dr. Carl Gans, 86, died peacefully after a long illness in Austin, Texas, on 30 November 2009. He was born in Hamburg, Germany, where he attended the Talmud Thora Realschule, and emigrated to the United States in 1939. Here he attended GeorgeWashington High School in New York City, received a Bachelor's Degree in Mechanical Engineering from New York University in 1944, a Master's Degree in Mechanical Engineering from Columbia University in 1950, a PE License from New York State in 1950, and a Doctoral Degree in Biology from Harvard in 1957. He served in the U.S. Army in the Pacific Command in the Philippines and Japan from 1944 to 1946. Carl was a John Simon Guggenheim Memorial Fellow from 1953 to 1955 conducting reptile studies in Brazil. After working eight years with Babcock & Wilcox installing power boilers, he changed careers and became a Professor of Biology and Department Chairperson at the University of Buffalo (later SUNY) from 1958 to 1971. He moved to Ann Arbor as Professor of Biology and Chairperson of Zoology at the University of Michigan until his retirement in 1998. Carl's work and hundreds of publications were in evolutionary physiology and comparative biomechanics. He carried out his primary studies in the area of reptiles and amphibians. He became world-known as editor of the journal "Morphology" for 25 years and as the editor of the monumental 23-volume "Biology of the Reptilia," published between 1969 and 2009. His first book-length publication was "Biomechanics" in which he combined his engineering and biology backgrounds. He co-authored two biology texts used in universities throughout the United States: "A Photographic Atlas of Shark Anatomy" and"Electromyography for Experimentalists." He also wrote the popular paperback book"Reptiles of the World," translated into many languages. His library of over 20,000 items in herpetology is currently at Ben Gurion University in Israel, which also has his extensive scientific correspondence. Other of his publications may be found at the Scripps Institute, University of California, San Diego, and the Museum of Comparative Zoology at Harvard. His extensive animal collections, which he gathered on five continents over many decades, can be found at the Field Museum of Natural History, Chicago, the California Academy of Sciences, San Francisco, the Carnegie Museum of Natural History, Pittsburg, and the Museum of Comparative Zoology at Harvard.
Carl was predeceased by his wife of fifty years, Mabel Kyoko Andow. He is survived by his brother Leo Gans of Teaneck, New Jersey.
*****
Memorial donations may be made to
THE CARL GANS AWARD
As some of you may be aware, we have been fund-raising for some time to endow the "Carl Gans Award," associated with the Division of Comparative Biomechanics, Society for Integrative and Comparative Biology (SICB). This award, recently approved by the SICB Executive Committee, is the first such award for the newly founded Division of Comparative Biomechanics and honors the numerous scientific and editorial contributions to biomechanics and herpetology by Carl Gans. To date, we have raised approximately two-thirds of the $25,000 required for endowment of this award. Fortunately, matching funds ($10,000) were generously made available by the late Carl Gans, his brother Leo Gans, and Sandy Gaunt that will provide a 2-for-1 match for the first $5000 contributed, no matter how small that, in conjunction with the matching offer, will let SICB takeadvantage of this new funding opportunity and enable the award to be established financially. Contributed funds should be marked for the "Carl Gans Award" and be sent to the attention of the SICB Executive Director, Brett Burk (BBurk@BurkInc.com) at the address below. He will deposit them into an account and reserve them for the fund. Send your contribution to:
Brett J. Burk SICB Executive Director 1313 Dolley Madison Boulevard, Suite 402 McLean, Virginia 22101
Contributions can also be made online at
https://ssl4.westserver.net/birenheide/secure/sicb/cart/donations.php
Osteology of the Middle Triassic Traversodontid Andescynodon
Liu, J., and J. Powell. 2009. Osteology of Andescynodon (Cynodontia:Traversodontidae) from the Middle Triassic of Argentina. American Museum Novitates 3674:1-19.
Abstract - All available specimens of Andescynodon mendozensis and Rusconiodon mignonei are examined and restudied, and the latter species is regarded as a junior synonym of the former. The postcranial skeleton of this species is described for the first time; it generally shows primitive features of traversodontids. Andescynodon mendozensis is a small- to medium-sized traversodontid characterized by 9~11 upper postcanines in adults (fewer in larger individuals), the transverse ridge of upper postcanines lying anteriorly on the tooth, paracanine fossa penetrating the skull roof in adult; it is differentiated from Pascualgnathus by relatively flatten skull, shorter and narrower temporal region, presence of four rather than three upper incisors.
Abstract - All available specimens of Andescynodon mendozensis and Rusconiodon mignonei are examined and restudied, and the latter species is regarded as a junior synonym of the former. The postcranial skeleton of this species is described for the first time; it generally shows primitive features of traversodontids. Andescynodon mendozensis is a small- to medium-sized traversodontid characterized by 9~11 upper postcanines in adults (fewer in larger individuals), the transverse ridge of upper postcanines lying anteriorly on the tooth, paracanine fossa penetrating the skull roof in adult; it is differentiated from Pascualgnathus by relatively flatten skull, shorter and narrower temporal region, presence of four rather than three upper incisors.
A Fun Book Is Now A Fun Exhibit
The Burke Museum of Natural History and Culture is excited to announce the opening of a new fossil exhibit. Cruisin’ the Fossil Freeway is an exhibit that brings together the best of the Burke Museum's fossil collection and the fossil-inspired artwork of celebrated artist Ray Troll to explore questions about evolution, extinction, and early life on Earth. The Burke Museum collaborated with artist Ray Troll and Seattle-born paleontologist Kirk Johnson to present this new exhibit exploring the abundance of fossils in our midst and how fossils shed light on Earth's past. Cruisin' the Fossil Freeway will travel nationally after closing in Seattle in late May 2010. The exhibit opens December 19. Please take a moment to visit the exhibits website at http://www.washington.edu/burkemuseum/cruisin/index.php.
Latest Literature - November 2009
Many recent and upcoming Triassic papers, mostly from Brazil.
Marynowski, L., and B. R. T. Simoneit. 2009. Widespread Upper Triassic to Lower Jurassic wildfire records from Poland:evidence from charcoal and pyrolytic polycyclic aromatic hydrocarbons. Palaios 24:785-798. DOI: 10.2110/palo.2009.p09-044r
Abstract - Laboratory tests indicate that 15% O2, instead of 12%, is required for the propagation of a widespread forest fire, a 3% increase from what was previously assumed. The presence of widespread wildfire records in the Upper Triassic and Lower Jurassic of Central Europe suggests that the lower limit for O2 during this time was at least 15%. Wildfire records are based on the co-occurrence of charcoal fragments and elevated concentrations of pyrolytic polycyclic aromatic hydrocarbons (PAHs). In all samples charcoal fragments are large to medium-sized and angular, suggesting that they were transported by rivers only short distances after charcoalification. Calculated combustion temperatures vary with stratigraphic position and average 295 377 uC, which is characteristic for ground or near-surface wildfires. The most extensive wildfires occurred in the earliest Jurassic and their intensities successively decreased with time. Average concentrations of the sum of pyrolytic PAHs for the lowermost Jurassic Zagaje Formation reached ~1253 mg/g total organic carbon (TOC), whereas for the Upper Triassic–Lower Jurassic Skłoby Formation they did not exceed ~16 mg/g TOC. Charcoal-bearing sequences were also characterized by the presence of phenyl-PAHs (Ph-PAHs) and oxygen-containing aromatic compounds. The dominance of the more stable Ph-PAH isomers in these immature to low-maturity sedimentary rocks supports their pyrolytic origin. The oxygenated PAHs may also be derived from combustion processes.
Veiga de Oliveira, T., Schultz, C. L., and M. B. Soares. 2009. A partial skeleton of Chiniquodon (Cynodontia, Chiniquodontidae) from the Brazilian Middle Triassic. Revista Brasileira de Paleontologia 12: 113-122. doi:10.4072/rbp.2009.2.02
Abstract - In this paper, we describe new postcranial remains of Chiniquodon cf. C. theotonicus, a chiniquodontid cynodont from the Therapsid Cenozone, from the Santa Maria Formation, Middle Triassic of Southern Brazil. In the described specimen are preserved almost all presacral vertebrae, the sacral vertebrae, an incomplete pelvic girdle, the left femur, and two metapodials. Some of these bones show slight differences relative to those already described for C. theotonicus, especially in the femur and in the pelvic girdle. Since the species can actually include the materials attributed to the genera Probelesodon (except from P. sanjuanensis) and Belesodon, however, these differences may represent normal ontogenetic variation in the species rather than being of taxonomically diagnostic value.
Stock Da-Rosa, A. A., Piniero, G., Dias-Da-Silva, S. Cisneros, J. C., Feltrin, F. F., and L. W. Neto. 2009. Bica São Tomé, a new fossiliferous site for the Lower Triassic of Southern Brazil. Revista Brasileira de Paleontologia 12:67-76. doi: 10.4072/rbp.2009.1.06
Abstract - Bica São Tomé, a new fossiliferous locality for the Sanga do Cabral Formation is described from southern Brazil. It consists in orange and reddish fine sandstones with sandy and calcareous concretions and intercalated fossiliferous intraformational conglomerates. This Lower Triassic locality is particularly interesting due to very well preserved and partially articulated specimens of continental tetrapods, an unusual feature in this unit, since the fossils in other outcrops are mostly disarticulated. Temnospondyl amphibians, procolophonoid and probable archosauromorph reptiles have been found in this new Lower Triassic locality. Further studies in this locality will allow the complement and a better acknowledged of the affinities of the Sanga do Cabral fauna with those from the basal Triassic Gondwanan and Laurasian.
De Amorim Arantes, B., Soares, M. B., and C. L. Schultz. 2009. Clevosaurus brasiliensis (Lepidosauria, Sphenodontia) from the Upper Triassic of Rio Grande do sul: post-cranial anatomy and phylogenetic relationships.Revista Brasileira de Paleontologia 12: 43-54. doi:10.4072/rbp.2009.1.04
Abstract - Sphenodontia is the most abundant taxon from the Caturrita Formation (Upper Triassic) paleofauna, which is composed predominantly by microvertebrates. However, only two syncrania (UFRGS-PV0613T e UFRGS-PV0748T) were formally described by Bonaparte & Sues in 2006 so far. Based on these materials, a new species Clevosaurus brasiliensis, was erected and the Clevosauridae family was formalized being composed by Clevosaurus, Brachyrhinodon and Polysphenodon. This work presents an anatomic description of the post-cranial skeleton of C. brasiliensis based on more than 25 specimens. Among the materials, dorsal, sacral and caudal vertebrae, femora, tibiae and fibulae were identified. Generally, the post-cranial skeleton presents the typical features of the sphenodontians, and the morphology of the bones is very similar to those of other species of Clevosaurus (e.g. C. hudsoni, C. bairdi). However, the adult individuals of the Brazilian species are notably smaller than most of the other sphenodontians. The anatomic information obtained was used, together with the cranial characters, in a phylogenetic analysis to establish the position of C. brasiliensis in the Sphenodontia clade. The data matrix was built with 18 taxa and 67 characters. The resulting cladogram confirms the close relationship between the Brazilian species with Clevosaurus hudsoni and attests the consistency of the Clevosauridae family.
Bardola, T. P., Schmidt, I. D., Sommer, M. G., and C. L. Schultz. 2009. Ginkgophyta wood in petrified forest of the Upper Triassic from Rio Grande do Sul, Brazil. Revista Brasileira de Paleontologia 12:139-148. doi:10.4072/rbp.2009.2.04
Abstract - The anatomic analysis of an assemblage of silicified fossil wood fragments from the Santa Maria Formation, southern Paraná Basin, Brazil, led to the identification of parameters compatible with the morphospecies Baieroxylon cicatricum, registered and described here for the first time for the Brazilian Gondwana. The secondary wood is homogeneous, picnoxylic and characterized by the presence of growth zones. In the radial walls of the tracheids there are bordered pits in a predominantly uniserial arrangement. Typical spiral thickening is present in longitudinal radial and tangential sections. The rays are in a uniserial arrangement and homogeneous. The cross-field pits, one to four per crossfield, are inconspicuous, circular, small and randomly arranged. Phloem and cortex are unpreserved. A common pattern found on the external surface of the wood fragments corresponds to simple eye-shaped scars, which would correspond to branch connections, and hollow, double and triple eye-shaped scars in alternating arrangement, which would correspond to leaf insertions.
Cabreira, S. F., and J. C. Cisneros. in press. Tooth histology of the parareptile Soturnia caliodon from the Upper Triassic of Rio Grande do Sul, Brazil. Acta Palaeontologica Polonica in press.
Abstract - A histological analysis of the dentition of the small procolophonid parareptile Soturnia caliodon reveals detailed information concerning tooth implantation and replacement for this taxon. The presence of acrodont tooth implantation is verified, which contradicts current models for procolophonid dentition. A heterogeneous enamel layer, that reaches large thickness on the cusps, and a broad secondary dentine are also recorded. These structures provide a very stable occlusal morphology that extends the useful life of the teeth. During the process of replacement, old teeth were not pushed out but reabsorbed. The evidence indicates that Soturnia caliodon had a very low rate of tooth replacement which constitutes a valuable adaptation for its high-fibre herbivorous niche.
Marynowski, L., and B. R. T. Simoneit. 2009. Widespread Upper Triassic to Lower Jurassic wildfire records from Poland:evidence from charcoal and pyrolytic polycyclic aromatic hydrocarbons. Palaios 24:785-798. DOI: 10.2110/palo.2009.p09-044r
Abstract - Laboratory tests indicate that 15% O2, instead of 12%, is required for the propagation of a widespread forest fire, a 3% increase from what was previously assumed. The presence of widespread wildfire records in the Upper Triassic and Lower Jurassic of Central Europe suggests that the lower limit for O2 during this time was at least 15%. Wildfire records are based on the co-occurrence of charcoal fragments and elevated concentrations of pyrolytic polycyclic aromatic hydrocarbons (PAHs). In all samples charcoal fragments are large to medium-sized and angular, suggesting that they were transported by rivers only short distances after charcoalification. Calculated combustion temperatures vary with stratigraphic position and average 295 377 uC, which is characteristic for ground or near-surface wildfires. The most extensive wildfires occurred in the earliest Jurassic and their intensities successively decreased with time. Average concentrations of the sum of pyrolytic PAHs for the lowermost Jurassic Zagaje Formation reached ~1253 mg/g total organic carbon (TOC), whereas for the Upper Triassic–Lower Jurassic Skłoby Formation they did not exceed ~16 mg/g TOC. Charcoal-bearing sequences were also characterized by the presence of phenyl-PAHs (Ph-PAHs) and oxygen-containing aromatic compounds. The dominance of the more stable Ph-PAH isomers in these immature to low-maturity sedimentary rocks supports their pyrolytic origin. The oxygenated PAHs may also be derived from combustion processes.
Veiga de Oliveira, T., Schultz, C. L., and M. B. Soares. 2009. A partial skeleton of Chiniquodon (Cynodontia, Chiniquodontidae) from the Brazilian Middle Triassic. Revista Brasileira de Paleontologia 12: 113-122. doi:10.4072/rbp.2009.2.02
Abstract - In this paper, we describe new postcranial remains of Chiniquodon cf. C. theotonicus, a chiniquodontid cynodont from the Therapsid Cenozone, from the Santa Maria Formation, Middle Triassic of Southern Brazil. In the described specimen are preserved almost all presacral vertebrae, the sacral vertebrae, an incomplete pelvic girdle, the left femur, and two metapodials. Some of these bones show slight differences relative to those already described for C. theotonicus, especially in the femur and in the pelvic girdle. Since the species can actually include the materials attributed to the genera Probelesodon (except from P. sanjuanensis) and Belesodon, however, these differences may represent normal ontogenetic variation in the species rather than being of taxonomically diagnostic value.
Stock Da-Rosa, A. A., Piniero, G., Dias-Da-Silva, S. Cisneros, J. C., Feltrin, F. F., and L. W. Neto. 2009. Bica São Tomé, a new fossiliferous site for the Lower Triassic of Southern Brazil. Revista Brasileira de Paleontologia 12:67-76. doi: 10.4072/rbp.2009.1.06
Abstract - Bica São Tomé, a new fossiliferous locality for the Sanga do Cabral Formation is described from southern Brazil. It consists in orange and reddish fine sandstones with sandy and calcareous concretions and intercalated fossiliferous intraformational conglomerates. This Lower Triassic locality is particularly interesting due to very well preserved and partially articulated specimens of continental tetrapods, an unusual feature in this unit, since the fossils in other outcrops are mostly disarticulated. Temnospondyl amphibians, procolophonoid and probable archosauromorph reptiles have been found in this new Lower Triassic locality. Further studies in this locality will allow the complement and a better acknowledged of the affinities of the Sanga do Cabral fauna with those from the basal Triassic Gondwanan and Laurasian.
De Amorim Arantes, B., Soares, M. B., and C. L. Schultz. 2009. Clevosaurus brasiliensis (Lepidosauria, Sphenodontia) from the Upper Triassic of Rio Grande do sul: post-cranial anatomy and phylogenetic relationships.Revista Brasileira de Paleontologia 12: 43-54. doi:10.4072/rbp.2009.1.04
Abstract - Sphenodontia is the most abundant taxon from the Caturrita Formation (Upper Triassic) paleofauna, which is composed predominantly by microvertebrates. However, only two syncrania (UFRGS-PV0613T e UFRGS-PV0748T) were formally described by Bonaparte & Sues in 2006 so far. Based on these materials, a new species Clevosaurus brasiliensis, was erected and the Clevosauridae family was formalized being composed by Clevosaurus, Brachyrhinodon and Polysphenodon. This work presents an anatomic description of the post-cranial skeleton of C. brasiliensis based on more than 25 specimens. Among the materials, dorsal, sacral and caudal vertebrae, femora, tibiae and fibulae were identified. Generally, the post-cranial skeleton presents the typical features of the sphenodontians, and the morphology of the bones is very similar to those of other species of Clevosaurus (e.g. C. hudsoni, C. bairdi). However, the adult individuals of the Brazilian species are notably smaller than most of the other sphenodontians. The anatomic information obtained was used, together with the cranial characters, in a phylogenetic analysis to establish the position of C. brasiliensis in the Sphenodontia clade. The data matrix was built with 18 taxa and 67 characters. The resulting cladogram confirms the close relationship between the Brazilian species with Clevosaurus hudsoni and attests the consistency of the Clevosauridae family.
Bardola, T. P., Schmidt, I. D., Sommer, M. G., and C. L. Schultz. 2009. Ginkgophyta wood in petrified forest of the Upper Triassic from Rio Grande do Sul, Brazil. Revista Brasileira de Paleontologia 12:139-148. doi:10.4072/rbp.2009.2.04
Abstract - The anatomic analysis of an assemblage of silicified fossil wood fragments from the Santa Maria Formation, southern Paraná Basin, Brazil, led to the identification of parameters compatible with the morphospecies Baieroxylon cicatricum, registered and described here for the first time for the Brazilian Gondwana. The secondary wood is homogeneous, picnoxylic and characterized by the presence of growth zones. In the radial walls of the tracheids there are bordered pits in a predominantly uniserial arrangement. Typical spiral thickening is present in longitudinal radial and tangential sections. The rays are in a uniserial arrangement and homogeneous. The cross-field pits, one to four per crossfield, are inconspicuous, circular, small and randomly arranged. Phloem and cortex are unpreserved. A common pattern found on the external surface of the wood fragments corresponds to simple eye-shaped scars, which would correspond to branch connections, and hollow, double and triple eye-shaped scars in alternating arrangement, which would correspond to leaf insertions.
Cabreira, S. F., and J. C. Cisneros. in press. Tooth histology of the parareptile Soturnia caliodon from the Upper Triassic of Rio Grande do Sul, Brazil. Acta Palaeontologica Polonica in press.
Abstract - A histological analysis of the dentition of the small procolophonid parareptile Soturnia caliodon reveals detailed information concerning tooth implantation and replacement for this taxon. The presence of acrodont tooth implantation is verified, which contradicts current models for procolophonid dentition. A heterogeneous enamel layer, that reaches large thickness on the cusps, and a broad secondary dentine are also recorded. These structures provide a very stable occlusal morphology that extends the useful life of the teeth. During the process of replacement, old teeth were not pushed out but reabsorbed. The evidence indicates that Soturnia caliodon had a very low rate of tooth replacement which constitutes a valuable adaptation for its high-fibre herbivorous niche.
Subscribe to:
Posts (Atom)