Some non-dino mammals papers with free pdfs...
Katrina E. Jones, Kenneth D. Angielczyk & Stephanie E. Pierce Â(2019)
Stepwise shifts underlie evolutionary trends in morphological complexity of the mammalian vertebral column.
Nature Communications 10, Article number: 5071
doi: Â
https://doi.org/10.1038/s41467-019-13026-3https://www.nature.com/articles/s41467-019-13026-3Free pdf:
https://www.nature.com/articles/s41467-019-13026-3.pdfA fundamental concept in evolutionary biology is that life tends to become more complex through geologic time, but empirical examples of this phenomenon are controversial. One debate is whether increasing complexity is the result of random variations, or if there are evolutionary processes which actively drive its acquisition, and if these processes act uniformly across clades. The mammalian vertebral column provides an opportunity to test these hypotheses because it is composed of serially-repeating vertebrae for which complexity can be readily measured. Here we test seven competing hypotheses for the evolution of vertebral complexity by incorporating fossil data from the mammal stem lineage into evolutionary models. Based on these data, we reject Brownian motion (a random walk) and uniform increasing trends in favor of stepwise shifts for explaining increasing complexity. We hypothesize that increased aerobic capacity in non-mammalian cynodonts may have provided impetus for increasing vertebral complexity in mammals.
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News:
Mammals' complex spines are linked to high metabolisms; we're learning how they evolved
Also, not yet mentioned:
Q&A with a Fossil Mammals Curator KENNETH ANGIELCZYKÂ
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Free pdf:
This article is a part of the thematic issue Memorial to StÃphane Peignà â Carnivores (Hyaenodonta and Carnivora) of the Cenozoic
We describe two large amphicyonid (Amphicyonidae, Carnivora) mandibles from Moghra, Early Miocene, Egypt. One of these represents a new species of Cynelos Jourdan, 1862, which is in the same size range as C. macrodon (Savage, 1965) and C. ginsburgi n. comb., but exhibits a relatively longer m1 paraconid blade. The other is allocated to Amphicyon giganteus (Schinz, 1825). Based on this new material the differences between Cynelos, Amphicyon Lartet in Michelin, 1836, and Afrocyon Arambourg, 1961 are clarified. We also reassign three (P4, M1, M2) of four isolated and unassociated amphicyonid teeth from Moghra, previously attributed to "Cynelos sp. nov." to Amphicyon giganteus. These teeth represent the first record of the upper dentition of A. giganteus from Africa. Enhanced diagnoses of Cynelos and Amphicyon also permit the reallocation of some other previously described specimens to these taxa. These include: assignment of Â"Amphicyon sp." and an isolated m2 previously identified as âAfrocyon burolleti Arambourg, 1961â from Gebel Zelten, Libya, to the new species of Cynelos; allocation of âYsengriniaâ ginsburgi from Arrisdrift, South Africa, to Cynelos ginsburgi n. comb.; and attribution of a giant undescribed additional species from Buluk, Kenya to Cynelos sp. Other specific specimens from Gebel Zelten and Kenya, currently assigned to Afrocyon, are also transferred to either Cynelos or Amphicyon. Results from this study, combined with previous work on the Moghra carnivores, suggests that at least three and perhaps as many as four very large carnivorous genera co-existed at Moghra: Cynelos, Amphicyon, Hyainailouros Stehlin, 1907 and possibly Megistotherium Savage, 1973. These giants represent the top predators of the Early Miocene of Africa, with Cynelos being more carnivorous, and Amphicyon, Hyainailouros and Megistotherium having more developed bone-crushing capabilities.