Meemannavis ductrix gen. et sp. nov.; Brevidentavis zhangi gen. et sp. nov. (1 Viewer)

[Fred Ruhe]

Jingmai K. O'Connor, Thomas A. Stidham. Jerald D. Harris, Matthew C. Lamanna, Alida M. Bailleul, Han Hu, Min Wang et Hailu You, 2022

Avian skulls represent a diverse ornithuromorph fauna from the Lower Cretaceous Xiagou Formation, Gansu Province, China

Journal of Systematics and Evolution. in press.
doi:10.1111/jse.12823

Abstract: https://onlinelibrary.wiley.com/doi/10.1111/jse.12823

We describe six specimens consisting of cranial remains and associated partial presacral axial series belonging to ornithuromorph birds from the Changma locality of the Lower Cretaceous Xiagou Formation of northwestern Gansu Province, China. Comparison among specimens is limited by the paucity of overlapping elements, their differing exposed views, and, in some specimens, poor preservation. Despite this, three separate taxa are represented, evidenced by differences in their dentary dentitions: one specimen is edentulous, another has sharp, closely spaced, relatively high-crowned and peg-like teeth, and a third preserves blunt, relatively low-crowned teeth placed in a communal groove, a morphology previously reported among adult birds only in Hesperornithiformes. We propose that the high-crowned specimen may be referred to Gansus yumenensis based on shared similarities with the closely related Iteravis huchzermeyeri, including a very similar dentition and an edentulous premaxilla with elongate, unfused frontal processes and no palatal processes. The two other specimens are considered new taxa, for which we erect the names Meemannavis ductrix gen. et sp. nov. and Brevidentavis zhangi gen. et sp. nov. These new specimens confirm that the Changma locality is dominated by ornithuromorph birds and contribute to a better understanding of this important avifauna. The observed variation in dental morphology hints at trophic diversity like that observed in ornithuromorphs from the penecontemporaneous Jehol Group of northeastern China.

Enjoy,

Fred

P.S. I hope someone is willing to send me the pdf of this paper, using WeTranfer, or to f,ruhe@upcmail,nl
Thanks in advance,

 

[Fred Ruhe]

I received the paper!!

Fred

 

[Fred Ruhe]

Remark: In the abstract and the description the authors mention the name Brevidentavis zhangi gen. et sp. nov. for specimen IVPP V26197). Unfortunately in the plates, the tables and the cladograms they use Brachydontornis zhangi n. sp. for IVPP V26197. I think this is a lable name and so it is a Nomen Nudum (no description or indication).

So I will ignore Brachydontornis zhangi n. sp. and use Brevidentavis zhangi gen. et sp. nov.

Fred

 

[Fred Ruhe]

Systematic Paleontology

AVES Linnaeus 1758
ORNITHUROMORPHA Chiappe 1999 [sensu O’Connor et al., 2016]
Genus Meemannavis gen. nov.

Meemannavis ductrix gen. et sp. nov.

Holotype Specimen: IVPP V26198, poorly preserved partial premaxillae and a possible maxilla and quadrate, a few possible palatal elements, complete orbital region and braincase prepared free from the sediment, nearly complete and articulated mandible, and partially articulated cervical and thoracic vertebrae preserved together with many small, unidentifiable, disarticulated fragments; bones are in various views and observations are obscured by a thick layer of applied consolidant

Locality and Horizon: Changma township, Yumen City, Jiuquan area, northwestern Gansu Province, China; Lower Cretaceous Xiagou Formation (lower Aptian).

Etymology: The generic name is in honor of the paleontologist Chang Meemann (张弥曼; also transliterated as Zhang Miman), -avis, Latin for bird; the epithet ‘ductrix,’ Latin meaning female leader, is in honor of her role as the first woman to serve as director of the IVPP (1984–1990), as a leader in her field in the study of fossil fish, and her role as mentor, role model, and inspiration to female scientists worldwide.

Diagnosis: Medium-sized ornithuromorph bird with the unique combination of the following features: premaxilla corpora fully fused; edentulous dentary that is dorsoventrally shallow, gently curved, and that gradually tapers rostrally; quadrate cotyles of the mandible rostrocaudally narrow. Can be differentiated from other Early Cretaceous ornithuromorphs with edentulous dentaries through the following morphologies: lacks the rostroventral expansion of the dentary seen in Archaeorhynchus and overall the dentary is more elongate in Meemannavis; mandibular symphysis that is present in Eogranivora is absent; dorsal surface of the dentary is gently concave (ventral surface gently convex), whereas it is straight in Xinghaiornis.


Fig. 1. Holotype of Meemannavis ductrix gen. et sp. nov. (IVPP V26198). A. Photograph. B. Interpretive drawings primarily in left lateral view. Scale bar equals ten millimeters. In A, inset at upper left is computed laminographic image confirming absence of dentary teeth; inset at lower right is orbital region and braincase in right lateral view. In B, inset is orbital region and braincase in right (top) and left (bottom) lateral views.

 

[Fred Ruhe]

Brevidentavis zhangi gen. et sp. nov.

Holotype specimen: IVPP V26197, both dentaries in dorsomedial view in articulation with the predentary, a pair of hyoid bones disarticulated away from their in vivo position, and approximately 12 articulated vertebrae exposed primarily in lateral view. A possible alimentary pellet is preserved partially overlain by the seventh preserved vertebra (Figure 4). Note that prior to this current in-depth study, this specimen was attributed to Gansus yumenensis in a paper that on focused the avian predentary (Bailleul et al., 2019a).

Locality and Horizon: Changma township, Yumen City, Jiuquan area, northwestern Gansu Province, China; Lower Cretaceous Xiagou Formation (lower Aptian).

Etymology: The generic name in Latin meaning short (brevis) tooth (dens) bird (avis) refers to the morphology of the dentary teeth; the specific epithet is in honor of Professor ZHANG Xing (张行, formerly of the Gansu Provincial Museum), co-leader of the 2002 expedition that rediscovered the Changma locality.

Diagnosis: Small-sized ornithuromorph bird with the unique combination of the following features: predentary present; dentary teeth located in a communal groove with interdental plates absent; teeth brachydont, approximately equal in crown height and mesiodistal length; and dentary teeth closely spaced, separated by a distance less than half their mesiodistal diameter. Can be differentiated from other ornithuromorphs in which the dentary teeth occur in a communal groove (hesperornithiforms) based on size (Brevidentavis much smaller), the morphology of the dentary teeth (crown morphology proportionately taller, recurved, and sharply tapered in hesperornithiforms), and the length of the tooth row (proportionately shorter and with fewer teeth in Brevidentavis).


Fig. 2. Holotype of Brevidentavis zhangi gen. et sp. nov. (IVPP V26197). A. Photograph. B. Interpretive drawing primarily in dorsal view. Scale bar equals ten millimeters. C. Computed laminographic images of dentaries in dorsomedial view. D. Computed laminographic images of dentaries in left ventrolateral views showing absence of interdental bone. Scale bars in equal two millimeters.

 

[Fred Ruhe]

cf. Gansus yumenensis

Specimen: IVPP V26199, a nearly complete skull, ventrally exposed, in articulation with the most cranial three cervical vertebrae. Numerous associated feathers are preserved both around the skull and in large patches nearby

Notes: We tentatively refer this specimen to G. yumenensis based on similarities with Iteravis and G. zheni


Fig. 3. Referred specimen cf. Gansus yumenensis (IVPP V26199). A. Photograph of entire specimen, showing extensive feather preservation. B. Photograph of skull and cranial cervical vertebrae, primarily in ventral view. C. Interpretive drawing of B. Scale bar equals 10 millimeters. D and E., Computed tomographic slices revealing the presence of teeth in the dentaries.

 

[Fred Ruhe]

Ornithuromorpha indet. A

Specimen: IVPP V26194, a skull preserving the most caudal portion of the rostrum and the orbital and postorbital regions in articulation with eight complete cervical vertebrae and the cranial portion of another, all elements exposed in dorsal view


Fig. 4. Specimen referred to Ornithuromorpha indet. A. (IVPP V26194). A. Photograph. B. Interpretive drawing in dorsal view. Scale bar equals 10 millimeters.

 

[Fred Ruhe]

Ornithuromorpha indet. B

Specimen: IVPP 26195, the caudal portion of a braincase with the interior surface exposed such that the raised surface of the labyrinth is visible; preserved in articulation with eight well preserved, ventrally exposed cervical vertebrae including the atlas and axis, plus the cranial portion of the ninth cervical.


Fig. 5. Specimen referred to Ornithuromorpha indet. B. (IVPP V26195). A. Photograph. B. Interpretive drawing primarily in ventral view. Scale bar equals five millimeters.

 

[Fred Ruhe]

Ornithuromorpha indet. C

Specimen: IVPP 26196, the orbital and postorbital region of a skull (including caudal portions of the mandible) in articulation with 15 vertebrae exposed largely in right lateral view; a shallow, poorly defined impression of rostral bones (suggesting a long, dorsoventrally narrow rostrum) is visible in the matrix


Fig. 6. Specimen referred to Ornithuromorpha indet. C. (IVPP V26196). A. Photograph. B. Interpretive drawing in right lateral view. Scale bar equals 10 millimeters.

 

[Fred Ruhe]

Cladogram

Fig. 7. Cladogram depicting the hypothetical relationships of the Xiagou ornithuromorph skulls relative to other Mesozoic bird taxa. A. Majority rule (>50) tree produced from 10,000 trees with lengths of 896 steps produced following two rounds of tree bisection reconnection (the first round produced a single well resolved tree of the same length with a consistency index of 0.367 and a retention index of 0.654) – values indicate the percentage of trees in which each node is resolved. B.the single tree (consistency index = 0.367; retention index = 0.654) produced when implied weighting was applied (k = 12).

Remark: Where Brachydontornis is mentioned read: Brevidentavis.

Fred