Topic
Pachygenelus
About: Pachygenelus is a research topic. Over the lifetime, 3 publications have been published within this topic receiving 92 citations.
Papers
TL;DR: This work suggests that synapsid columnar enamel structure was easily transformed into plesiomorphic prismatic enamel (PPE) and that PPE may be described with at least five independent character states, and proposes that appearance of a prism sheath transforms SCE into PPE.
Abstract: Characters from enamel microstructure have not been used in recent phylogenetic analyses of Mesozoic Mammalia. Reasons are that enamel characters have been perceived as (A) variable without regard to systematic position of taxa, (B) inconsistently reported within the literature, and (C) simply scored as either prismatic or not prismatic in earlier mammals. Our work on Mesozoic mammals such as Sinoconodon, Gobiconodon, Triconodontidae, Docodon, Laolestes, and others suggests that synapsid columnar enamel (SCE) structure was easily transformed into plesiomorphic prismatic enamel (PPE) and that PPE may be described with at least five independent character states. Two PPE characters—a flat, open prism sheath and a planar prism seam—were present in the cynodont Pachygenelus and in several Jurassic and Cretaceous mammals. We propose that appearance of a prism sheath transforms SCE into PPE and that reduction and loss of a prism sheath reverse PPE into SCE, in both phylogeny and ontogeny. We further propose that no amniote vertebrates other than the trithelodontid cynodont, Pachygenelus, plus Mammalia have ever evolved an ameloblastic Tomes process capable of secreting PPE and that the genetic potential to secrete PPE is a synapomorphy of Pachygenelus plus Mammalia, whether or not all lineages of the clade have expressed that potential.
43 citations
TL;DR: Elliotherium is a tritheledontid from the lower Elliot Formation (Upper Triassic; Euskelosaurus Range Zone) on the farm Beatrix, Free State Province, South Africa.
Abstract: We describe a new tritheledontid, Elliotherium kersteni n. gen. and sp., on the basis of a partial skull collected from the lower Elliot Formation (Upper Triassic; Euskelosaurus Range Zone) on the farm Beatrix, Free State Province, South Africa. Although similar to Pachygenelus, the genus differs from other South African tritheledontids in its higher maxillary postcanine tooth count, lack of labial cingula on the upper postcanine teeth, shorter secondary palate, retention of a median vomerine ridge behind the secondary palate, and smaller interpterygoid vacuity. With regard to these features, Elliotherium is most similar to the South American tritheledontid Chaliminia. Elliotherium is autapomorphic in its possession of a long parasphenoid rostrum, ventrally depressed secondary palate, medially convex margins of the interpterygoid vacuity, and a thin lamina of palatine covering the interpterygoid vacuity. Although Elliotherium is the stratigraphically lowest positioned tritheledontid from southern Africa, it is still probably later occurring than the South American taxa Chaliminia or Riograndia. Based on a revision of a previous analysis of advanced cynodont relationships, we propose a sister-group relationship between Elliotherium and Chaliminia, although support for this pairing is weak.
40 citations
TL;DR: In this article, the authors recovered a semi-elliptical burrow cast in the Lower Jurassic upper Elliot Formation (Stormberg Group) on the farm Edelweiss 698 (Free State).
29 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2017 | 1 |
| 2006 | 1 |
| 1999 | 1 |