Anserimimus Barsbold, 1988
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publication ID |
https://doi.org/ 10.4202/app.2009.1123 |
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persistent identifier |
https://treatment.plazi.org/id/C87AE97D-3417-B232-FFAF-66F2FDE1F353 |
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treatment provided by |
Felipe |
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scientific name |
Anserimimus Barsbold, 1988 |
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Genus Anserimimus Barsbold, 1988
Type species: SPS GIN AN MPR 100/300, Bugin−Tsav , Upper Senonian (all according to Barsbold (1988); in the present text it is referred as GIN 100 /300) .
aff. Anserimimus planinychus Barsbold, 1988
Figs. 2–9 View Fig View Fig View Fig View Fig View Fig View Fig View Fig View Fig .
Material.— ZPAL MgD−I/65, associated partial axial skeleton with hind− and forelimb elements; ZPAL MgD−I/66, forelimb elements; ZPAL MgD−I/23, ZPAL MgD−I/231, ZPAL MgD−I/233, unguals of the manus.
Stratigraphic and geographic range.— The specimen was collected in Tsagan Khushu locality (near Bugin Tsav which is the type locality of Anserimimus planinychus ) in the Nemegt Formation, Ömnogöv Province, Mongolia ( Fig. 1 View Fig ). Additional specimens were collected in the vicinity of the ZPAL MgD−I/65 but were not directly associated with the skeleton .
The sediments of the Tsagan Khushu are considered to be Late Cretaceous in age (lower Campanian or?upper Campanian–?lower Maastrichtian; see Gradziński 1970; Gradziński et al. 1977; Karczewska and Ziembińska−Tworzydło 1983; Jerzykiewicz 2000).
Description
Axial skeleton.—The vertebral column of ZPAL MgD−I/65 is very incomplete ( Fig. 2 View Fig ). Available vertebrae are represented by their centra, mainly without anterior articular surfaces. The odontoid of the putative axial vertebra is oval and subtriangular in anterior view, and it has a flat ventral surface. The centrum of this vertebra is slender, antero−posteriorly long, and ventrally flat. The preserved posterior articular surface of the next preserved cervical vertebra is concave, subrectangular and with a gently convex dorsal edge. A preserved part of the centrum indicates that the anterior articular surface has been elevated in relation to the posterior articular surface. The next centrum in the cervical series, preserved with a fragmentary vertebral arch that has a deep posterior ligament scar, demonstrates the same feature, with the same elevation of the anterior articular surface as in the previous one. On the basis of comparisons with Gallimimus bullatus Osmólska, Roniewicz, and Barsbold, 1972 , the latter two centra should be placed in the region of the 3rd–5th vertebrae in the neck region. The articular surfaces of the following centra, which are also ventrally flat, do not have the elevation. The most complete cervical centrum is the penultimate one. In comparision with the vertebrae of G. bullatus , it is the ninth cervical centrum. Its body is antero−posteriorly (ratio of vertebral body height (VBH)/vertebral body length (VBL) equals approximately 0.4) long and it is flat ventrally. The posterior articular surface of the centrum, in contrast to the anterior surface, is dorso−ventrally low. The next preserved centrum, probably the tenth cervical, consists only of its posterior half. The fragment has a small keel on its ventral surface that indicates that it was a transitional vertebra between the cervical and dorsal regions.
The next preserved of the available centra, comparing to G. bullatus and GIN 96091KD ( Kobayashi 2004: fig. 20), is considered as one of the first dorsals. All dorsal centra are spool shaped, and their articular surfaces tend to be enlarged and become more rounded posteriorly.
The sacrum is represented only by one centrum which is massive, spool shaped and flat ventrally with the articular surface of the subsequent vertebra firmly attached to it. Its anterior articular surface is rectangular, and posterior one is oval, with the vertical axis being the longest. Along the ven−
doi:10.4202/app.2009.1123
tral side of the centrum there is a scar that is widest at the contact with the subsequent vertebra. The dorsal side of the centrum is abraded and it is unclear whether or not the neurocentral suture was fully closed.
The caudals are similar to those in Gallimimus bullatus . Their centra are spool shaped with oval articular surfaces and with a ventral oblong scar, which widens and deepens towards both ends of the vertebrae. The scar is restricted laterally (at the contact of the centra) with processes that end with articular surfaces for the hemal arches.
Forelimb.—The preserved portion of the Mtc I ( Fig. 3F View Fig ) is dorso−ventrally flat, and it is subtriangular in cross−section.On its lateral side there is a concave surface to contact with Mtc II.
Mtc II is the best preserved among available metacarpal bones ( Fig. 3E View Fig ). It is dorso−ventrally flat, subrectangular in cross−section at its midpoint, and subtriangular at the proximal and distal end. On its medial side there is a flat surface to contact Mtc I (it occupies approximately 62% of the medial side). The distal half of Mtc II extends laterally at an angle of about 23 °. The lateral side of Mtc II has a concavity to contact Mtc III, that is shallower than is seen in G. bullatus . The proximal articular surface of Mtc II is triangular in shape. The distal joint surface is ball shaped, constituting ball and socket articulation between the metacarpal and the first phalanx−a feature characteristic of Ornithomimidae ( Kobayashi and Lü 2003) . The distal articular surface is twisted clockwise at an angle of about 26 ° in relation to the proximal joint surface. The proximal articular surface of Ph I−1 ( Fig. 3C View Fig ) is oval in outline, slightly laterally flattened with a wide ventral scar. Both proximal and distal articular surfaces of Ph II−2 ( Fig. 3B View Fig ) have a hinge joint with Ph II−1 and Ph II−3, a feature typical for interphalangeal joints of the manus and pes. On the ventral side of the distal half of Ph II−2 there is a transversely oval cavity. Ph III−3 ( Fig. 3A View Fig ) is similar to Ph II−2, but its articular surfaces are smaller. Both phalanges, contrary to the holotype of Anserimimus planinychus , are almost equal in length.
The manual ungual of the referred material is almost straight (curvature is slight), and have flat ventral surfaces similar to the condition seen in A. planinychus (see Barsbold 1988) ( Fig. 5 View Fig ). The flexor tubercle is low with a coarse ventral surface, and is set far distally relative to the joint surface. At the lateral and medial sides there are deep grooves, these are sometimes penetrated by vascular foramina.
Pelvic girdle and hind limb.—The proximal part of the left pubis is preserved ( Fig. 6 View Fig ). Despite the lack of some portions of the bone it displays the typical configuration for ornithomimids with a larger ischial peduncle. On the medial side of the ischial peduncle there is a concavity that is shallower than is seen in Gallimimus bullatus . On the anterior edge of the pubis, slightly laterally, a rugosity is present, developed almost throughout the length of the specimen. It is abraded just below the attachment surface for the pubic peduncle of the ilium. The remaining part of the structure, which is identified as the origin of M. ambiens (Osmólska et al. 1972), is rough, indicating a well developed muscle. Only two fragments of the right femur have been collected from the Tsagan Khushu; the blade of the lesser trochanter ( Fig. 7A View Fig ) and the distal region with deep depression on the anterior side that is eroded, but it has a sharp crest on its medial side above the distal condyle ( Fig. 7B View Fig ). Ph II−1 is laterally flattened ( Fig. 8B View Fig ). On its ventral surface there is a deep scar. The distal articular surface of Ph II−1 firmly attaches to Ph II−2 ( Fig. 8A View Fig ). Both phalanges indicate a presence of the typical hinge joint.
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Ph III−1 is dorso−ventrally flat ( Fig. 8D View Fig ). Its proximal articular surface is concave, subrectangular with a convex dorsal edge. Ventrally there is a scar surrounded by crests, like those present on Ph II−1. Nevertheless, both scar and crests are smaller than in Ph II−1. The distal articular surface of the Ph III−1 is transversely wide with deep ligament pits. Both proximal and distal articular surfaces of the Ph III−2 represent hinge joints. Digit four is the most complete ( Fig. 9 View Fig ). The lateral condyles of all the phalanges are taller than medial ones. The ungual is short, ventrally flat, subtriangular in cross−section, and slightly curved, with grooves laterally. The state of preservation of the rest of the ZPAL MgD−I material does not provide any additional anatomical information.
| ZPAL |
Zoological Institute of Paleobiology, Polish Academy of Sciences |
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