Similiyanornis brevipectus sp. nov. and Abitusavis lii sp. nov. (1 Viewer)

[Fred Ruhe]

Min Wang , Zhiheng Li , Qingguo Liu & Zhonghe Zhou, 2020

Early Cretaceous ornithuromorph birds provide insights into the taxonomy and divergence of Yanornithidae (Aves: Ornithothoraces)

Journal of Systematic Palaeontology. 18 (21): 1805–1827.
doi:10.1080/14772019.2020.1836050

Abstract:

https://www.tandfonline.com/doi/abs/10.1080/14772019.2020.1836050?journalCode=tjsp20

Yanornithidae is an Early Cretaceous ornithuromorph clade that preserves the oldest direct evidence indicative of a piscivorous diet in avian evolution. The family hitherto contained only a single genus Yanornis and two putative species. The yanornithids are readily distinguishable from other Mesozoic avians in having a long rostrum packed with numerous teeth. Despite the discoveries of dozens of specimens, little is known about the taxonomical and ecomorphological diversity of this clade due to a lack of comparative studies. Here, we describe two new yanornithid taxa, Similiyanornis brevipectus gen. et sp. nov. and Abitusavis lii gen. et sp. nov., based on two nearly complete skeletons from the Early Cretaceous Jehol Biota. We perform a taxonomical reassessment of yanornithids and rectify the assignments of published putative Yanornis-like materials. The results show that Yanornithidae contains three genera and three species, which demonstrate a wide range of limb proportions that exceed the degree seen in other L early ornithuromorph clades.

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Fred

 

[Fred Ruhe]

Systematic palaeontology

Class Aves Linnaeus, 1758
Ornithothoraces Chiappe, 1995
Ornithuromorpha Chiappe, 2002
Family Yanornithidae Zhou & Zhang, 2001

Type genus. Yanornis Zhou & Zhang, 2001.

Included genera. Yanornis Zhou & Zhang, 2001, Similiyanornis gen. nov., Abitusavis gen. nov.

Stratigraphical range. Yixian and Jiufotang formations (Aptian, Lower Cretaceous).

Geographical range. Liaoning Province and Inner Mongolia, north-eastern China.

Emended diagnosis of family. Pintail-sized (Anas acuta) ornithuromorph birds differing from other ornithuromorphs in the unique combination of the following features: elongate skull with a length/height ratio of approximately 2; toothed upper and lower jaws; dentary bearing subparallel dorsal and ventral margins and approximately 20 teeth; cervical vertebrae elongate; sternum with a pair of caudal fenestrae; radius bearing bicipital tubercle; proximoventral margins of ungual phalanges of alular and major digits step-like without flexor processes; ischium nearly straight and probably lacking a dorsal process; and proximal pedal phalanges longer than distal ones.

Phylogenetic definition. No phylogenetic definition has yet been proposed by previous studies, and here we suggest that Yanornithidae is the most inclusive clade containing Yanornis martini Zhou & Zhang, 2001 and Abitusavis lii gen. et sp. nov., but not Yixianornis grabaui Zhou & Zhang, 2001, Piscivoravis lii Zhou, Zhou & O’Connor, 2014a or Passer domesticus Linnaeus, 1758.

Genus Yanornis Zhou & Zhang, 2001
Yanornis martini Zhou & Zhang, 2001

Type species. Yanornis martini Zhou & Zhang, 2001

Synonymy. Yanornis guozhangi Wang, Ji, Teng & Jin, 2013.

Holotype. IVPP V12558, a complete and articulated skeleton preserved in a single slab.

Referred material. IVPP V13358, V12444

Occurrence and age. Chaoyang City, Yixian Country, Liaoning Province, north-east China; Jiufotang Formation, Lower Cretaceous

Revised diagnosis of Yanornis martini. A yanornithid bird differentiated from other yanornithids on the basis of the following unique combination of characters: premaxillary corpus longer than maxillary process of premaxilla; dentary with a vertically oriented rostral margin; coracoid with a rectangular procoracoid process; sternum bearing a pair of craniolateral processes and a pair of caudal fenestrae; caudal end of lateral trabeculae expanded; synsacrum containing nine sacrals and bearing a ventral groove; bicipital crest of humerus with a pit-shaped fossa; and elongate forelimb with an intermembral index of 1.27.

Genus Similiyanornis gen. nov.

Type species. Similiyanornis brevipectus sp. nov.

Diagnosis. As for the type and only species.

Derivation of name. The generic name is derived from Greek prefix ‘simil’ to indicate similar morphology with Yanornis martini.

Similiyanornis brevipectus sp. nov.

Holotype. IVPP V13278, a complete skeleton associated with feathers

Derivation of name. The specific name is derived from Latin ‘brevi’ (short) and ‘pectis’ (sternum), referring to the relatively short sternum.

Occurrence and age. Xierhuqiao Village, Yixian Country, Jinzhou City, Liaoning Province, northeast China; Jiufotang Formation, Lower Cretaceous (Aptian; He et al. 2004).

Diagnosis. A relatively small yanornithid ornithuromorph bird characterized by the unique combination of the following features: maxillary process of premaxilla shorter than premaxillary corpus; ‘T’-shaped lacrimal bearing slender caudal ramus; dentary having a minute alveolus near the rostral tip; two surangular fenestrae; first dentary tooth hypertrophied; proximal phalanx of major digit over two-thirds of carpometacarpus length; elongate femur 85% the tibiotarsus length; and enlarged flexor process of ungual phalanx of digit IV. The new species can be further differentiated from other yanornithids by the following features: premaxillary corpus bearing a large foramen (absent in Yanornis martini); prezygapophyses longer than postzygapophyses in cervical vertebrae (opposite condition in Yanornis martini and Abitusavis lii); medial margin of procoracoid process less expanded proximodistally than in Yanornis martini and Abitusavis lii; and bicipital crest of humerus without a pit-shaped fossa (present in Yanornis martini).

Remarks. IVPP V13278 was previously referred to Yanornis martini (Zhou et al. 2004).

 

[Fred Ruhe]

Genus Abitusavis gen. nov.

Type species. Abitusavis lii sp. nov.

Diagnosis. As for the type and only species.

Derivation of name. The name is derived from Latin 'abitus’ (departure), ‘avis’ (bird).

Abitusavis lii sp. nov.

Holotype. IVPP V14606, a nearly complete skeleton

Referred material. IVPP V13259.

Derivation of name. The name is in memory of the late Mr Yutong Li, a IVPP senior technician who dedicated his whole career to the preparation of many important non-avian dinosaur and bird fossils.

Occurrence and age. Ningcheng Country, Inner Mongolia, China; Yixian Formation, Lower Cretaceous (Aptian) (Zhou & Zhang 2005).

Diagnosis. A large-sized yanornithid ornithuromorph bird distinguished by the unique combination of the following characters: dorsocaudally elongate retroarticular process; synsacrum comprising eight sacrals and bearing a ventral groove; lateral trabeculae of sternum not expanded caudally; metatarsals II and III both bearing a dorsal tubercle for the M. cranialis tibialis; distal vascular foramen proximally located; and proximoventral margins of ungual phalanges of pedal digits step-like without flexor processes. The new taxon is further differentiated from other yanornithids by the following features: procoracoid process of coracoid rectangular in shape (triangular in Similiyanornis brevipectus); sternum without craniolateral processes (present in Yanornis martini and Similiyanornis brevipectus); and intercotylar eminence of tarsometatarsus absent (present in Yanornis martini and Similiyanornis brevipectus).

Fred

 

[Fred Ruhe]

Figure 1. Holotype of Similiyanornis brevipectus gen. et sp. nov. (IVPP V13278). A, photograph; B, interpretive drawing. Abbreviations: ald, alular digit; ce, cervical vertebra; dv, dorsal vertebra; fu, furcula; lco, left coracoid; lfe, left femur; lfi, left fibula; lhu, left humerus; lil, left ilium; lis, left ischium; lpu, left pubis; lrd, left radius; lsc, left scapula; lta, left tarsometatarsus; lti, left tibiotarsus; lul, left ulna; mad, major digit; mid, minor digit; pd, pedal digit; pg, pygostyle; rcm, right carpometacarpus; rco, right coracoid; rfe, right femur; rhu, right humerus; ril, right ilium; ris, right ischium; rpu, right pubis; rrd, right radius; rta, right tarsometatarsus; rti, right tibiotarsus; rul, right ulna; sk, skull; sy, synsacrum. Scale bars represent 10mm.

Figure 2. Holotype of Abitusavis lii gen. et sp. nov. (IVPP V14606). A, photograph; B, interpretive drawing. Abbreviations: ald, alular digit; ce, cervical vertebra; dv, dorsal vertebra; fu, furcula; lcm, left carpometacarpus; lco, left coracoid; lfe, left femur; lfi, left fibula; lhu, left humerus; lil, left ilium; lpu, left pubis; lrd, left radius; lta, left tarsometatarsus; lti, left tibiotarsus; lul, left ulna; mad, major digit; mid, minor digit; pd, pedal digit; pg, pygostyle; rcm, right carpometacarpus; rco, right coracoid; rfe, right femur; rhu, right humerus; rpu, right pubis; rqu, right quadrate; rrd, right radius; rsc, right scapula; rta, right tarsometatarsus; rfi, right fibula; rti, right tibiotarsus; rul, right ulna; sk, skull; st, sternum; sy, synsacrum. Scale bars represent 10mm.

Fred