Musivavis amabilis gen. et sp. nov. (1 Viewer)

[albertonykus]

Wang, X., A. Cau, X. Luo, M. Kundrát, W. Wu, S. Ju, Z. Guo, Y. Liu, and Q. Ji (2022)
A new bohaiornithid-like bird from the Lower Cretaceous of China fills a gap in enantiornithine disparity
Journal of Paleontology (advance online publication)
doi: 10.1017/jpa.2022.12

A new enantiornithine, Musivavis amabilis n. gen. n. sp., is reported from the Lower Cretaceous Jehol Biota in western Liaoning, China. The new taxon is similar to the bohaiornithids in the robust subconical teeth, bluntly expanded omal ends of the furcula, caudolaterally oriented lateral trabeculae with triangular distal ends of the sternum, and a robust second pedal digit. Yet it differs from members of Bohaiornithidae in several features recalling other enantiornithine lineages, such as the acuminate rostral ramus of maxilla, the shape of the coracoid lateral margin, the presence of craniolateral processes on the sternum, the proportions of the manual phalanges, and the unspecialized third pedal ungual phalanx. A comprehensive phylogenetic analysis of Mesozoic birds shows that homoplasy significantly affects the reconstruction of enantiornithine relationships. When all phylogenetic characters are considered of equal weight, Musivavis is reconstructed in a lineage related to a radiation of large-bodied enantiornithines including Bohaiornithidae and Pengornithidae. Alternative scenarios based on progressive downweighting of the homoplastic characters support more basal placements of the pengornithids among Enantiornithes, but do not alter the affinity of Musivavis as a member of the “bohaiornithid-grade” group.

 

[Fred Ruhe]

Systematic paleontology

Avialae Gauthier, 1986
Pygostylia Chiappe, 2002
Ornithothoraces Chiappe, 1995
Enantiornithes Walker, 1981
Genus Musivavis new genus

Type species.—Musivavis amabilis n. gen. n. sp., only known species, from the Aptian of northeastern China.

Diagnosis.—As for the type species, by monotypy.

Etymology.—The generic name is derived from the Latin “musivum” (mosaic, decoration with small stone tesserae) and “avis” (bird).

Remarks.—As for the type species.

Musivavis amabilis new species

Holotype and only known specimen.—MHGU-3000, a nearly complete and articulated skeleton preserved in a single slab.

Diagnosis.—Musivavis amabilis n. gen. n. sp. can be referred to Enantiornithes by possessing several synapomorphies of this clade, such as the sternum with nearly equal length and width, the “Y”-shaped furcula with a long hypocleideum, the minor metacarpal extending farther distally than the major metacarpal, and the fourth metatarsal relatively thin (Chiappe and Walker, 2002). It can be further referred to the “Bohaiornithidae-grade” group by possessing some of the diagnostic features of this family, such as the subconical teeth with tapered and slightly caudally recurved tips, the sternum with lateral trabecula projected caudolaterally, the omal end of furcular ramus with blunt expansion, and the tapered pygostyle without abrupt distal constriction (M. Wang et al., 2014). It is distinguishable from the bohaiornithids by possessing the following unique combination of features (local autapomorphies denoted by asterisks): the pygostyle abruptly tapers distally (shared with Gretcheniao); the sulcus excavating the epicleideal ramus of the furcula is very deep and extends distally onto the proximal third of the hypocleideum*; a sharp keel runs along the whole ventral surface of the
furcula, from the junction of the epicleideal rami to the distal tip of the hypocleideum; the flat cranial margin of the sternum becomes curved near the craniolateral process*; the sternum possesses craniolaterally projected craniolateral
processes* (in bohaiornithids, only Zhouornis possesses craniolateral processes, which project laterally); the xiphoid process of the sternum extends nearly to the same level of the distal end of the lateral trabecula and expands as a blunt
distal end (shared with Bohaiornis); and the first alular phalanx bears a transversally expanded proximal end followed by a gracile shaft, resulting in a concave proximomedial corner of the bone*.

Occurrence.—The holotype was recovered from the Lower Cretaceous Jiufotang Formation (Aptian) at Shangheshou locality, Chaoyang City, Liaoning Province, China.

Etymology.—The specific name is derived from the Latin “amabilis” (lovely or beautiful), referring to the exquisite preservation of the holotype.

Remarks.—Musivavis amabilis n. gen. n. sp. is much smaller in size than currently known bohaiornithids and pengornithids, and differs from the comparably sized cathayornithids (e.g., Cathayornis, Hebeiornis, Sinornis) in the following features: omal tips of furcula transversely expanded; sternum with craniolateral processes and expanded, triangular-shaped distal end of the lateral trabecula (both features absent in Hebeiornis); deltopectoral crest less prominent relative to humerus shaft (more developed in Cathayornis and Sinornis); minor metacarpal not strongly bowed posteriorly, resulting in a slit-like intermetacarpal space (distinctly bowed in Cathayornis and Sinornis, resulting in a larger intermetacarpal space); ungual phalanx of major digit more curved than the alular ungual phalanx (less curved in Hebeiornis); distal end of metatarsal II subequal in width to distal end of metatarsal III (wider in Hebeiornis and Sinornis); poorly developed flexor tubercles in the pedal ungual phalanges (more prominent in Hebeiornis and Sinornis).

Fred


Figure 1. Holotype (MHGU-3000) of Musivavis amabilis n. gen. n. sp. from the Early Cretaceous Jiufotang Formation (Aptian). (1) photograph; (2) line drawing.
Abbreviations: al, alular metacarpal; ald, alular digits; an, angular; cav, caudal vertebrae; cv, cervical vertebrae; d, dentary; fu, furcula; fr, frontal; hy, hyoid; il, ilium;
lco, left coracoid; lfe, left femur; lfi, left fibula; lh, left humerus; lr, left radius; lsc, left scapula; lti, left tibiotarsus; ltm, left tarsometatarsus; lu, left ulna; m, maxilla;
m-Ⅰ–Ⅳ, metatarsal Ⅰ-Ⅳ; mac, major metacarpal; mad, major manual digits; mic, minor metacarpal; mid, minor manual digits; n, nasal; pa, parietal; pd-Ⅰ–Ⅳ,
pedal digitⅠ-Ⅳ; pr, premaxilla; pu, pubis; py, pygostyle; rco, right coracoid; rfe, right femur; rfi, right fibula; rh, right humerus; rl, radiale; rr, right radius; rsc, right
scapula; rti, right tibiotarsus; ru, right ulna; se, semilunate carpal; sr, scleral ring; st, sternum; su, surangular; syn, synsacrum; ul, ulnare.

Figure 2. The effect of homoplastic characters in enantiornithine relationships. Two alternative topologies obtained setting an aggressive (left) or moderate (right)
downweighting of the characters according to their homoplasy. Note, in particular, the radically different placements of the pengornithids (blue branches) under the
two alternative weighting settings. On the contrary, Musivavis n. gen. (bold) is consistently found among the least inclusive clade containing the bohaiornithid-like
taxa (red). Avisauridae, Longipterygidae, and Ornithuromorpha collapsed for brevity.