Benutzer:A11w1ss3nd/Kongonaphon
Kongonaphon is an extinct genus of lagerpetid avemetatarsalians from the mid to late Triassic of Madagascar. It is known from the "basal Isalo II beds" and is notable for its diminutive size, even compared to other small early avemetatarsalians.[1]
Description
The maxilla is tall and has a relatively wide front portion when seen from above. Six teeth are preserved in the maxilla, though the rear part of the bone is missing. The teeth were peg-like and conical, with a circular cross-section. The teeth are ornamented by irregular pitting, a texture which in modern animals is correlated with a diet of insects. A limb bone fragment has been tentatively identified as the lower part of a humerus. This fragment has poorly differentiated condyles (unlike the humerus of Ixalerpeton) but is also markedly asymmetrical (like Ixalerpeton).[1]
The femur is very slender, sigmoid, and has a prominent fourth trochanter. The femoral head shares many similarities with other lagerpetids. It is strongly hooked and has a concave emargination on its lower edge. When seen from above, the femoral head has a large posteromedial tuber, a small anterolateral tuber, and no anteromedial tuber. The upper part of the femur also has an anterior trochanter, a feature which only develops in fully grown individuals of certain lagerpetid species (namely Dromomeron gregorii and Ixalerpeton polesinense). The blade-like fourth trochanter has a bent inner edge and an outer edge which smoothly transitions to the shaft of the femur. Both of these features are more similar to Ixalerpeton than Lagerpeton (or Dromomeron, which has a small, mound-like fourth trochanter). The bent inner edge of the fourth trochanter overlooks a depression which is split in two by a thin ridge. The femur is extended and narrows significantly towards its (broken and eroded) lower extremity, unlike other lagerpetids which have a femur that expands towards the knee.[1]
Tibia fragments are slightly curved and expanded near the knee, similar to other lagerpetids. A pair of long and closely-appressed bones have been identified as metatarsals, though this is uncertain due to the unusually bent appearance of one of the bones. Pedal phalanges (toe bones) are hourglass-shaped and have strongly developed joints. The very long and thin caudal (tail) vertebra has a concave lower edge and fused neurocentral sutures.[1]
References
- ↑ a b c d Christian F. Kammerer, Sterling J. Nesbitt, John J. Flynn, Lovasoa Ranivoharimanana, André R. Wyss: A tiny ornithodiran archosaur from the Triassic of Madagascar and the role of miniaturization in dinosaur and pterosaur ancestry. In: Proceedings of the National Academy of Sciences. 2. Juli 2020, ISSN 0027-8424. doi:10.1073/pnas.1916631117.
