Zhelestes temirkazyk, NESOV, 1985
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publication ID |
https://doi.org/ 10.1111/j.1096-3642.2011.00771.x |
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persistent identifier |
https://treatment.plazi.org/id/AB4D878F-FFAB-6120-51E1-FCF7C035FC65 |
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Marcus |
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scientific name |
Zhelestes temirkazyk |
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ZHELESTES TEMIRKAZYK NESOV, 1985 A
FIGURES 21–23 View Figure 21 View Figure 22 View Figure 23
(See Appendix 4 for synonymies, referred illustrations, and referred specimens.)
Holotype: CCMGE 10 View Materials /12176, left maxilla with heavily worn P2, P3 (now broken), P4-5, M1-3 and alveoli for C, P1. Found in 1980.
Type locality and horizon: CBI-17, Dzharakuduk, Kyzylkum Desert, Uzbekistan. Bissekty Formation, Upper Cretaceous (middle- upper Turonian).
Revised diagnosis: Differs from Aspanlestes and Parazhelestes by upper and lower canine singlerooted; mandibular condyle above alveolar level; p5 paraconid cingulid cusp or absent. Differs from Aspanlestes , Parazhelestes , and Eoungulatum by diastema between upper canine and premolars present; diastema posterior to P1 present; P3 singlerooted. Differs from Parazhelestes and Eoungulatum by protocone labial shift absent. Differs from Parazhelestes by mandibular symphysis at p3 or more posterior; trigonid angle between 36–49°. Differs from Eoungulatum by P5 protocone smaller than paracone; P5 metacone swelling; P5 para- and metastylar lobes subequal; upper molar preparastyle present; metacone slightly smaller than paracone; ‘coronoid’ facet absent; masseteric fossa bordered ventrally by welldefined crest connected to condyle; m3 subequal to larger than m2.
Description: Maxilla. The maxilla is almost completely preserved in the type specimen ( Fig. 21 View Figure 21 ). In structure it is quite similar to the maxilla URBAC 02–45 of Aspanlestes ( Fig. 6 View Figure 6 , see description above), and preserves a more complete palatal process. The proportions are somewhat different, which may be related to size differences between the specimens. The facial process is relatively shorter and higher; it is highest above P4 ( Fig. 21A View Figure 21 ). Its anterodorsal corner is inflated and has a large hole for the canine root. In Aspanlestes there is no such inflation. A thin anterior projection of the facial process, covering the canine laterally and present in URBAC 02–45, is not preserved in CCMGE 10/12176. Dorsal to the broken area an intact bone edge is preserved, suggesting that at least part of the lateral alveolus for the canine was formed by the premaxilla. The infraorbital foramen is placed higher and relatively further backward compared with URBAC 02–45, above the distal root of P4. The palatal process is quite narrow (widest at the level of P4) and slightly convex ventrally. The anterior end of the palatal process projects anteriorly beyond the canine alveolus, as in Aspanlestes . The intermaxillary suture is straight. The maxillopalatine suture extends from a level between P4 and P5 to the posterior end of the bone. Here the medial border of the palatal process is convex and approximates the molar’s alveoli. The jugal facet is wide posteriorly and tapers anteriorly to the level between P4 and P5. Its widest part is between M2 and M3 (above M 3 in Aspanlestes ). The lacrimal facet is not discernible.
Upper dentition. The upper canine is not known, but judging from its alveolus in the holotype maxilla it was large, single-rooted, and quite curved throughout its length. The anterior premolars or their alveoli are known only from the type specimen, representing a quite old individual. The P1 was mesiodistally aligned with other premolars. The alveolus for its mesial root is more than twice as small as the alveolus for the distal root and confluent with the canine alveolus. In Nesov et al. (1998: fig. 10) P1 was reconstructed as single-rooted, but we think that it more likely had two roots. The P2 is a relatively large conical tooth with two roots and without distinct accessory basal cusps. P3 is small, peg-like, and single-rooted; the crown is now missing but can be seen in previous photos (e.g. Nesov et al., 1998: fig. 9A). P3 is separated by a small diastema from P2 and by a twice longer diastema from P4. The posterior upper premolars and molars are heavily worn in all known specimens. The structure of P4-5 is essentially the same as in Parazhelestes . In an isolated P4 URBAC 98–117 there is a better-developed anterior accessory cusp. The upper molars are similar to those of Parazhelestes in morphology, but differ in proportions: they are relatively wider labiolingually and more mesiodistally constricted at the centre. In M2 URBAC 02–81 there are some crenulations on the ectocingulum. The M3 is as wide labiolingually as M2 (narrower than M 2 in P. robustus ).
Dentary. There are two anterior mental foramina: one is at the anterior end of the canine alveolus, just beneath the i4 alveolus, another is under the mesial root of p1 (CCMGE 3/11658, ZIN 88480). The posterior mental foramen is under the distal root of p5 (ZIN 88480). The masseteric crest is strong and there are multiple labial mandibular foramina (ZIN 88453, 88461, and other specimens). The mandibular symphysis is quite long, with the posterior end at the level between the roots of p2 (juvenile specimen ZIN 88469), or between p2 and p3 (adult specimen ZIN 88480). The Meckelian groove is absent (ZIN 88461). In the juvenile specimen ZIN 88469 the angular and part of the condylar processes are preserved ( Fig. 22A View Figure 22 ). The condyle was probably not fully ossified and was placed significantly above the alveolar level. The angular process is constructed as in Aspanlestes and P. mynbulakensis with only a slight lingual inflection.
Lower dentition. In a young specimen, CCMGE 3/11658, with an erupting canine ( Fig. 22B View Figure 22 ), there are alveoli for four incisors, with i3 largest and i4 smallest. In an older edentulous dentary ZIN 88480, the alveoli for i1-3 are similar in size and the alveolus for i4 is much smaller and confined within the canine alveolus. The lower canine was large and single-rooted (ZIN 88480). CCMGE 3/11658 preserves the crown of the erupting lower canine ( Fig. 22B View Figure 22 ).
Judging from alveoli in edentulous dentaries (e.g. ZIN 88461 and 88480), p1 and p3 were double-rooted and smaller than p2, but not as reduced as in Parazhelestes . In ZIN 88461 there is a relatively large diastema between p2 and p3.
The p2 is known from a dentary fragment CCMGE 3/11658 ( Fig. 22B View Figure 22 ). The central cusp is conical and slightly turned distally. There are no mesial accessory cusps and only a small distal accessory cusp. The roots are swollen and spread apart. It is possible that this tooth could be a dp2 because the canine in this dentary fragment is at the initial stage of erupting. An unerupted crown of p2 is also present in ZIN 82555.
The p5 is known from three specimens, the isolated tooth CCMGE 2/12953 and unerupted crowns in dentary fragments URBAC 03–218 and ZIN 88448 ( Fig. 22C–E View Figure 22 ). CCMGE 2/12953 is unique amongst p5s of Dzharakuduk’s zhelestids in having a very small, cingulid paraconid, which is placed very low on the crown. It is not preserved and may not have been present on the two other p5s, where this portion of the crown was not fully formed and is now missing. A cingulid-like paraconid on p5 may have been a consistent feature of Zhelestes , whereas in P. mynbulakensis it is a trigonid cusp. In this character Zhelestes is very similar to Borisodon . The p5 of Zhelestes is clearly distinct from that tooth in Borisodon in having a metaconid, present in all three known specimens. The small talonid basin lingual to the talonid ridge is somewhat more expanded than in Borisodon . In URBAC 03–218 there is a small second talonid cusp, the entoconid (absent in CCMGE 2/12953; in ZIN 88448 this part of the crown is missing). In CCMGE 2/12953 there is a well-developed, distolabial cingulid.
The lower molars of Zhelestes are similar to those of other Dzharakuduk zhelestids, but differ from the lower molars of Parazhelestes in having a larger trigonid angle, which is presumably correlated to mesiodistally narrower upper molars in Zhelestes compared to Parazhelestes . The best-preserved m1 is CCMGE 37/12000 ( Fig. 23A View Figure 23 ). The trigonid angle is slightly greater that in m2 and m3. The paraconid is more labially shifted than in m2 or m3, and is smaller than this cusp in m2 but larger than in m3. The precingulid is ridge-like, as in P. mynbulakensis .
The m2 trigonid has a lesser angle than m1 or m3, whereas the paraconid is the larger and more lingually placed. The sample of m2s is more numerous than for other lower molars and shows more variation. The most variable structures are the precingulid and postcingulid. The labial cingulid is complete, connecting the precingulid and the postcingulid in URBAC 98–15; very short, confined to the hypoflexid area in URBAC 06–26; or absent in other specimens. URBAC 04–309 has the best-developed precingulid amongst the sample, but the postcingulid is totally lacking in this specimen ( Fig. 23B View Figure 23 ). The postcingulid is the strongest in URBAC 02–35 and 02–65.
There are two unerupted m3s represented by two unerupted crowns in dentary fragments (URBAC 03–218, ZIN 88448; Fig. 22E View Figure 22 ). The m3 is best known from an isolated and worn specimen CCMGE 3/12953 ( Fig. 23D View Figure 23 ). The trigonid is constructed as in m1 except that the paraconid is even smaller. The precingulid is quite small. The talonid is longer and narrower than the trigonid. The talonid is quite damaged so was probably originally somewhat wider. All three talonid cusps are similar in size. The hypoconulid is about equidistant from the hypoconid and the entoconid.
Measurements: See Appendices 2 and 3.
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