Field of Science

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.

4 comments:

  1. Woo! Now we need someone to describe "Nyasasaurus". Btw, the supposed palatal teeth of the new Massospondylus species turned out to be from a fish, right?

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  2. Mickey - the new Massospondylus species in JVP is from South Africa. I believe the specimen you're thinking of is the supposed Massospondylus skull from the Kayenta Fm, which Attridge et al. 1985 (JVP) described as having palatal teeth. That specimen is currently being redescribed by Hans-Dieter Sues, but it has yet to be published. Don't know what the verdict is on the palatal teeth.

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  3. No palatal teeth in M. kaalae I'm afraid...

    As for Nyasasaurus, watch this space...

    ReplyDelete
  4. D'oh! You're right, I was thinking of the Kayenta one. As for "Nyasasaurus", exciting.

    ReplyDelete

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