AI Article Synopsis

  • The specimen of Saurodesmus robertsoni, discovered in the 1840s, was misclassified over time and is now reexamined as a femur of a derived cynodont, potentially linked to the Tritylodontidae family.
  • The study identifies specific traits shared between Saurodesmus and other related cynodonts, emphasizing its unique anatomical features and positioning within evolutionary history.
  • This research underscores the importance of re-evaluating historical specimens, which could enhance our understanding of evolutionary relationships in ancient species.

Article Abstract

Predating Darwin's theory of evolution, the holotype of Saurodesmus robertsoni is a long-standing enigma. Found at the beginning of 1840s, the specimen is a damaged stylopodial bone over decades variably assigned to turtles, archosaurs, parareptiles, or synapsids, and currently nearly forgotten. We redescribe and re-assess that curious specimen as a femur and consider Saurodesmus robertsoni as a valid taxon of a derived cynodont (?Tritylodontidae). It shares with probainognathians more derived than Prozostrodon a mainly medially oriented lesser trochanter and with the clade reuniting tritylodontids, brasilodontids, and mammaliaforms (but excluding tritheledontids) the presence of a projected femoral head, offset from the long axis of the femoral shaft; a thin, plate-like greater trochanter; a distinct dorsal eminence proximal to the medial (tibial) condyle located close to the level of the long axis of the femoral shaft and almost in the middle of the width of the distal expansion; and a pocket-like fossa proximally to the medial (tibial) condyle. Saurodesmus robertsoni is most similar to tritylodontids, sharing at least with some forms: the relative mediolateral expansion of the proximal and distal regions of the femur, the general shape and development of the greater trochanter, the presence of a faint intertrochanteric crest separating the shallow intertrochanteric and adductor fossae, and the general outline of the distal region as observed dorsally and distally. This makes Saurodesmus robertsoni the first Triassic cynodont from Scotland and, possibly, one of the earliest representatives of tritylodontids and one of the latest non-mammaliaform cynodonts worldwide. Moreover, it highlights the need for revisiting historical problematic specimens, the identification of which could have been previously hampered by the lack of adequate comparative materials in the past.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC11135747PMC
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0303973PLOS

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Article Synopsis
  • The specimen of Saurodesmus robertsoni, discovered in the 1840s, was misclassified over time and is now reexamined as a femur of a derived cynodont, potentially linked to the Tritylodontidae family.
  • The study identifies specific traits shared between Saurodesmus and other related cynodonts, emphasizing its unique anatomical features and positioning within evolutionary history.
  • This research underscores the importance of re-evaluating historical specimens, which could enhance our understanding of evolutionary relationships in ancient species.
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