Zhalmouzia bazhanovi Averianov and Archibald, 2014
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publication ID |
https://doi.org/ 10.4202/app.2011.0143 |
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persistent identifier |
https://treatment.plazi.org/id/AA15E617-FFBB-FFB2-FCC7-65C4FAD0F991 |
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treatment provided by |
Felipe |
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scientific name |
Zhalmouzia bazhanovi Averianov and Archibald |
| status |
sp. nov. |
Zhalmouzia bazhanovi Averianov and Archibald sp. nov.
Fig. 2A View Fig .
Etymology: Named after Valerian Semenovich Bazhanov (1907–1984), who described B. orlovi from Shakh Shakh.
Holotype: ZIN 100639 View Materials , left dentary fragment with m2–3 and alveoli for c, p1–5, and m1.
Type locality: Shakh Shakh 2 locality of Malakhov et al. (2009) [= Shakh Shakh I of Rozhdestvensky 1964], about 70 km northeast of Dzhusaly railway station, Kyzylorda Province, Republic of Kazakhstan. Type horizon: Bostobe Formation (Late Cretaceous, Santonian–?Campanian).
Diagnosis.— Zhalmouzia bazhanovi is referred to Zhelestidae because the protoconid in this specimen is subequal to the para- and/or metaconid, the protocristid is transverse, and the hypoconulid closely approximates the entoconid. Z. bazhanovi differs from Avitotherium Cifelli, 1990 because the paraconid is not on the lingual margin of the tooth, and from Borisodon Archibald and Averianov, 2012 in the presence of a rounded mesiolingual vertical crest of the paraconid and the absence of the Meckelian groove; differs from Borisodon , Gallolestes Lillegraven, 1976 , and Eozhelestes Nesov, 1997 in having a trigonid less than twice the height of the talonid, and from Gallolestes , Avitotherium , and Parazhelestes Nesov, 1993 in a trigonid angle of 36–49° (as opposed to 35° or less in the latter taxa); differs from Borisodon and Parazhelestes in having the mandibular symphysis extending to the level of p3 or further posteriorly; differs from Eozhelestes in having a protoconid subequal to the para- and/ or metaconid, and a cristid obliqua contacting the protocristid labial to the protocristid notch; differs from Avitotherium and Eozhelestes in having a transverse protocristid, and from Gallolestes in having a mesiolabial cuspule f with a distinct cingular shelf. Z. bazhanovi resembles Eoungulatum Nesov, Archibald, and Kielan-Jaworowska, 1998 , and differs from all other zhelestids in having an ultimate lower molar smaller than the penultimate one (the state of this character is unknown for Avitotherium ). Z. bazhanovi differs from Eoungulatum in having a short and erect hypoconulid on the ultimate lower molar, and because the ventral border of the masseteric fossa is present as a well-defined crest. Finally, Z. bazhanovi differs from all other known zhelestids in having a posteriormost mental foramen located below the penultimate premolar (state unknown in Avitotherium ).
Description. —The horizontal ramus of the dentary of ZIN 100639 gradually tapers anteriorly, but its depth slightly increases at the canine alveolus. However, only the posterior margin of the canine alveolus is preserved, and it is not clear if the canine was single or double-rooted. The bone surface of this specimen is also somewhat abraded, and the articular surface of the mandibular symphysis is poorly defined; nevertheless, it appears that the symphysis terminates at the mesial root of p3. On the labial surface of the dentary, there is a small mental foramen below the mesial root of p1, close to the alveolar border. The posterior mental foramen is distinctly larger and is located below the distal root of p4, closer to the mid-height of the ramus than the anterior foramen.
The postcanine alveoli are closely spaced. The alveoli for p1 are slightly rotated relative to the long axis of the dentary, while the alveoli for the other postcanine teeth are in line with this axis. All the premolars are double-rooted and the relative sizes of their alveoli are as follows: p1 <p2> p3 <p4> p5. The total length of the p4 alveoli is greater than that of p5, while the individual alveoli for the p4 roots are smaller than those for p5. As in other zhelestids and Paranyctoides , p3 is the smallest premolar, although p1 is only slightly larger. Although only a small part of the coronoid process is preserved, there is some space between the last molar and the coronoid process, suggesting that this animal was fully mature. The masseteric fossa is deep; it is bordered anteriorly by a laterally flared coronoid crest, and ventrally by a low, wide crest extending across less than half of the depth of the horizontal ramus. Within the masseteric fossa, there is a single labial mandibular foramen of moderate size. The ventral margin of the horizontal ramus is gently convex below m2–3 and the base of the coronoid process, but straight below m1 and the premolars.
The lower molars (m2–3) are hardly worn and almost completely preserved, except for the missing apex of the protoco-
Zhalmouzia nid of m2. The preserved molars are similar in morphology, but differ in size: m3 is about 10% shorter and narrower than m2. Additionally, the m2 talonid is relatively more expanded than in m3 and wider than the trigonid, whereas the opposite is true for m3. The trigonid is moderately compressed (trigonid angle is ~42° in m2 and 47° in m3). The protoconid (unworn in m3) is only slightly higher than the metaconid. The paraconid is less than half the height of the metaconid and is offset from the lingual margin of the crown. The trigonid basin is filled by the bases of the trigonid cusps and is closed lingually. The protocristid is nearly transverse, with a wide angle between the protocristid arms, while the paracristid is more angled on m3 than on m2, with a smaller angle between the arms. The precingulid is a prominent shelf extending along most of the mesial side of the crown, and lingually abuts the hypoconulid of the preceding tooth. The talonid is about half the height of the trigonid. The talonid basin is extensive and rather deep, with its deepest point being adjacent to the protocristid notch. The cristid obliqua terminates somewhat labial to the protocristid notch. The hypoconid is the largest talonid cusp. The entoconid is taller than the hypoconid, but because the crown is higher labially than lingually, the total height of hypoconid is greater than that of the entoconid. The hypoconulid is only slightly smaller than the entoconid and closer to the latter than to the hypoconid (a feature related to the labiolingual expansion of the talonid). On m3, the hypoconulid is short, erect i.e., not procumbent distally), and relatively larger and locat- ed somewhat more distally than on m2. The labial postcingulid is faint, but rather long; on m2, its wear matches that of the m3 precingulid. The labial cingulid is extremely faint and hardly recognizable. The distal root of m3 is only a little longer (mesiodistally) than the mesial root.
Measurements (all measurements in mm).—ZIN 100639, m2, L = 1.8, TRW = 1.3, TAW = 1.3; m3, L = 1.6, TRW = 1.2, TAW = 1.1.
Remarks.—The lower molars of the holotype of Beleutinus orlovi from Shakh Shakh ( Fig. 2B View Fig ) are heavily abraded, preventing us from comparing the molar morphologies of these two taxa. The holotype of B. orlovi is about 25–30% larger than ZIN 100639 and likely belongs to a distinct taxon. In B. orlovi , the distal root of m3 is labiolingually compressed and longer than the mesiodistally compressed mesial root, while in ZIN 100639 both roots are of similar size. B. orlovi was referred provisionally to Zalambdalestidae ( Nesov 1987; Nesov et al. 2004), but this assignment was later challenged in light of the fragmentary nature of the only known specimen ( Wible et al. 2004). In its large size and laterally compressed distal root of m3, B. orlovi is similar to the zhelestid Eoungulatum from the Turonian of Uzbekistan ( Archibald and Averianov 2012), but differs in having a relatively larger m3. Beleutinus orlovi should be considered a nomen dubium, not identifiable beyond Eutheria indet.
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