Wednesday 2 July 2014

Two new species on Enantiornithine Birds from the Jehol Biota.

The deposits of the Jehol Group in northeastern China have yielded a spectacular number of fossil Birds and closely related non-Avian Theropod Dinosaurs over the past three decades. The most numerous and diverse group of Birds in this assemblage are the Enantiornithines, toothed Birds related but not ancestral to the modern Neornithine Birds, with about 27 separate species described from numerous specimens. 

In a paper published in the journal Vertebrata PalAsiatica on 21 January 2014, Wang Min of the Key Laboratory of Vertebrate Evolution and Human Origins at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences and the University of Chinese Academy of Sciences, Zhou Zhong-He and Jingmai O’Connor, also of the Key Laboratory of Vertebrate Evolution and Human Origins and Nikita Zelenkov of the Borissiak Palaeontological Institute of the Russian Academy of Sciences describe two new species of Enantiornithine Birds from the Jehol Biota.

The first new Bird species is named Parabohaiornis martini, where ‘Parabohaiornis’ means ‘similar to Bohaiornis’ (a previously described species of Enantiornithine Bird) and ‘martini’ honours the late Larry Martin, a distinguished palaeontologist and expert on avian evolution. Parabohaiornis martini is described from two specimens, from the Jiufotang Formation at Lamadong in Jianchang County in Liaoning Province.

The first specimen of Parabohaiornis martini is complete and partially articulated, and appears to be from a subadult, as not all the bones are fully fused. The second appears to be from a fully mature individual, but lacks the head and the wings below the elbow joint.

Photograph and line drawing of Parabohaiornis martini. Abbreviations: alm. alular metacarpal; al 1, 2. alular digit phalanx 1, 2; cav. caudal vertebrae; co. coracoid; cv. cervical vertebrae; dr. dorsal rib; dt. distal tarsal; fe. femur; fi. fibula; fu. furcula; ga. gastralia; hu. humerus; il. ilium; is. ischium; ma 1, 2, 3. major digit phalanx 1, 2, 3; mam. major metacarpal; mi 1. minor digit phalanx 1; mim. minor metacarpal; mt I–IV. metatarsal I, II, III, IV; pd. pedal digits; pt. proximal tarsals; pu. pubis; py. pygostyle; r. radius; ra. radiale; sc. scapula; sem. semilunate carpal; sk. skull; sr. sternal rib; st. sternum; sy. synsacrum; ti. tibia; tv. thoracic vertebrae; u. ulna; ul. ulnare. Wang et al. (2014).

Parabohaiornis martini is a medium sized, robust Enantiornithine Bird with three robust conical teeth on each premaxilla and four more on each maxilla. 

Photograph and line drawing of the second specimen of Parabohaiornis martini. Abbreviation: fv. vertebrae of fish; other abbreviations follow the top image. Wang et al. (2014).

The second new species is named Longusunguis kurochkini, where ‘Longusunguis’ means ‘long-claw’ and ‘kurochkini’ honours the late Evgeny Kurochkin, a distinguished palaeontologist and expert on fossil Birds. Longusunguis kurochkini is described from a single specimen, again from the Jiufotang Formation at Lamadong. The specimen is complete and articulated, though the head is detached. It also appears to be a subadult.

Longusunguis kurochkini is a medium-sized Enantiornithine Bird with robust conical teeth and long, curved claws.

Photograph and line drawing of Longusunguis kurochkini. Abbreviations: par. parapophyses; pot. posterior trochanter; other abbreviations follow the top image. Wang et al. (2014).

Parabohaiornis martini and Longusunguis kurochkini appear to be closely related, as well as also being closely related to the previously described Bohaiornis, Shenqiornis, Sulcavis and Zhouornis. Wang et al. suggest that these Birds should be grouped together to form a separate family within the Enantiornithine, which they name as the Bohaiornithidae.

All members of the Bohaiornithidae appear quite similar, being roughly medium sized (for Enantiornithine Birds), robust conical teeth and strong feet with long, curved claws. This suggests that they occupied a distinct ecological niche, though the exact nature of this was impossible to determine. 

The tough elongate feet of the Bohaiornithidae are typical of ground-living Birds today, but this seems unlikely due to their curved claws. Claws like those seen in the Bohaiornithidae are seen in the modern Raptors, as well as in Birds that habitually climb of tree-trunks. However tree-trunk climbing Birds typically have a number of specialized features on their hindlimbs, none of which are present in the Bohaiornithidae. Nor do they appear well suited for hunting like Raptors, as the proportions of their feet are quite different, and their teeth appear adapted for a durophagous diet.

See also…

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Birds derived from small Theropod Dinosaur ancestors in the Middle Jurassic, and appear to have reached similar levels of diversity in the Cretaceous to that seen today. However the dominant group of Birds in the Cretaceous were the Enatiornithines, a group of toothed Birds related to but not ancestral to modern Birds (Ornithuromorpha), which died out...

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