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A new specimen of Parabohaiornis martini (1 Viewer)

Fred Ruhe

Well-known member
Netherlands
Min Wang, 2023

A new specimen of Parabohaiornis martini (Avialae: Enantiornithes) sheds light on early avian ly avian skull evolution

VERTEBRATA PALASIATICA 61: 90.-107

Abstract and free pdf:
file:///C:/Users/Fred/Downloads/A%20new%20specimen%20of%20Parabohaiornis%20martini%20(Avialae%20Enantiornithes)%20sheds%20light%20on%20early%20avian%20skull%20evolution-1.pdf

The Enantiornithes is the most speciose clade of Mesozoic avialans with over 60 named taxa reported from most continents that span the whole Cretaceous. Most of the fossil remains of this clade, as well as those of other early diverging avialans are preserved in two dimensions. This complicates efforts to extract detailed anatomical information from the skull, in which the composite elements are delicate and thus not easily observable through conventional methods. The scarcity of well-preserved early avialan skulls, as well as the limited number of specimens that have been analyzed using computed tomography scanning, consequently circumscribes a large morphological gap in the fossil record during the transition from the heavy and akinetic dinosaurian skull to the lightweight and kinetic bird skull. Here, we present a three-dimensional digital reconstruction of the skull and part of the cervical vertebrae of a new specimen
of the enantiornithine Parabohaiornis martini from the Early Cretaceous of China. Our results demonstrate that Parabohaiornis retains the plesiomorphic non-avialan dinosaurian temporal and palatal configurations, reinforcing the recent hypothesis that the temporal and palatal regions are evolutionarily conservative and that the akinetic skull has been conserved well into diversification of early branching avialans.

Enjoy,

Fred
 
Systematic paleontology

Avialae Gauthier, 1986
Ornithothoraces Chiappe, 1995
Enantiornithes Walker, 1981
Bohaiornithidae Wang et al., 2014a
Parabohaiornis martini Wang et al., 2014a

Revised diagnosis

A medium-sized bohaiornithid enantiornithine that is distinguishable from other bohaiornithids in preserving the following combination of characters (asterisk marks autapomorphy): maxilla bearing four teeth; nasal perforated by a foramen*; concave dorsal margin of lacrimal*; surangular bearing a lateral fossa*; scapular with an acromion process oriented in parallel to the shaft in lateral view; tibiotarsus without an intercondylar incisure; length ratio of pygostyle to metatarsal III of 0.92–0.99; and a proximal phalanx of pedal digit IV proportionately shorter than in other bohaiornithids relative to the penultimate phalanx of digit IV (this ratio <70% in Parabohaiornis, but >80% in other bohaiornithids)
(modified from Wang et al., 2014a)

Remarks

IVPP V28398 is larger than the two known specimens of Parabohaiornis: specifically, the humerus is 21% and 12% longer than the holotype IVPP V18691 and the referred specimen V18690, respectively (Figs. 1,2; Table 1). The new specimen is also considered to be more osteologically mature than those two specimens based on the complete fusion of all its compound elements, most notably the fusion of the tibiotarsus and tarsometatarsus which remain unfused in V18690 and V18691.

Fred


Fig. 1 Photograph of the new referred specimen of Parabohaiornis martini, IVPP V28398
Abbreviations: ald. alular digit; am. alular metacarpal; ca. caudal vertebra; ce. cervical vertebra; co. coracoid; dv. dorsal vertebra; fe. femur; fi. fibula; fu. furcula; hu. humerus; hy. hyoid; il. ilium; is. ischium; ma. major metacarpal; mad. major digit; mi. minor metacarpal; mid. minor digit; pu. pubis; py. pygostyle; p-I to p-IV. pedal digit I to IV; ra. radius; sc. scapula; sk. skull; st. sternum; sy. synsacrum; ti. tibiotarsus; tm. tarsometatarsus; un. ulna; /r(l). right (left) side.
Scale bar = 20 mm
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