Daulestes inobservabilis ( Nessov, 1982 )

Archibald, J. David & Averianov, Alexander O., 2006, Late Cretaceous asioryctitherian eutherian mammals from Uzbekistan and phylogenetic analysis of Asioryctitheria, Acta Palaeontologica Polonica 51 (2), pp. 351-376 : 357-359

Daulestes inobservabilis ( Nessov, 1982)

Figs. 3 , 4 , Tables 1, 2.

1982 Taslestes inobservabilis sp. nov.; Nessov 1982: 235, pl. 1: 4.

1991 Taslestes inobservabilis ; Nessov and Kielan−Jaworowska 1991: fig. 1.

1993 Mixotheridia [indet.]; Nessov 1993: figs. 5(7) and 6(1).

1994 Taslestes inobservabilis ; Nessov et al. 1994: 57, pl. 1: 4.

1997 Taslestes inobservabilis ; Nessov 1997: pl. 46: 8, pl. 55: 3.

1997 Kennalestes (?) uzbekistanensis sp. nov.; Nessov 1997: 166, pl. 50: 1.

2000 Taslestes inobservabilis ; Averianov 2000: fig. 30.4E.

2000 Kennalestes sp. nov.; Averianov 2000: fig. 30.5R.

2000 Daulestes inobservabilis [comb. nov.]; McKenna et al. 2000: 6.

Holotype: CCMGE 8 /11758, right dentary with worn m2 and alveoli for

m1 and m3. Found in 1979.

Type locality and horizon: CDZH− 17g, Dzharakuduk, Kyzylkum Desert,

Uzbekistan. Bissekty Formation, Upper Cretaceous (Turonian).

Referred specimens.— URBAC 98–146 , right P4 missing small part of anterior margin (CBI−14) ; URBAC 02−91 , right maxilla with P5, M1, and alveoli for P4 and M2–3 (CBI−4e) ; URBAC 04−153 , right maxilla with M1 and alveoli for P5 and M2 (CBI−14) ; URBAC 03−18 , left maxilla with M1 (CBI−14) ; URBAC 98−140 , left M2 (CBI−14) ; URBAC 99−102 , labial part of a right M2 (CBI−14) ; URBAC 99−103 , labial part of a right M2 (CBI−14) ; URBAC 98−138 , lingual part of left M1 or 2 (CBI−14) ; ZIN 84972 , right dentary with p5, posterior alveolus for p1, and alveoli for double−rooted p2, 4 (CBI−14, 1987) ; URBAC 03−88 , left dentary with p5, m1–3, and posterior root of p4 (CBI−14) ; CCMGE 72 /12455, left dentary with m2 [now damaged but can be seen in Nessov’s photographs] and alveoli for m1 and m3 (the holotype of Kennalestes ? uzbekistanensis Nessov, 1997, CBI−4e, 1989) ; URBAC 00− 43, right dentary with alveoli for p1–2, 4, dp5?, m1–3, and erupting m3 (CBI−14); ZIN 88441 , left dentary with alveoli for p4–5, m1–2 (CBI−5a, 1989) ; URBAC 00−55, left dentary with alveoli for p4–5, m1 (CBI−14).

Revised diagnosis.—Similar to D. kulbeckensis but averaging 5.7% (range of 12% smaller – 23% larger) larger based on measurements of m1 and m2 and averaging 4.5% (range of 0–8%) larger based on measurements of M1 and M2.

Description.—The most complete maxillary fragment is URBAC 02−91 with P5, M1 and partial alveoli for P4 and M2–3 ( Fig. 3B ). On the labial side there appears to be a jugal facet from the middle of M1 toward the posterior end of the fragment. In URBAC 04−153 there is an infraorbital foramen dorsal to P4.

P4 ( Fig. 3A ) is very high, with anterior and posterior crests, and small anterior and posterior cusps. The base of labial side of the crown is nearly straight. There are a complete lingual cingulum and a small lingual swelling just posterior of the middle of the crown. This swelling is supported by the posterior root, which is slightly subdivided. Thus there are two roots, with the posterior of the two being slightly larger.

The P5 is a semimolariform, three−rooted tooth ( Fig. 3B ). There is a small but distinct metacone swelling on the postparacrista. The paracone is large and occupies a central position on the crown. The ectoflexus is deep and the labial margin is almost symmetrical with prominent metastylar and parastylar lobes. There is no stylocone or preparastyle and the preparacrista connects to a rather large parastyle. The trigon is transversely wide and anteroposteriorly narrow, with a prominent but low protocone. There are no conules or lingual cingula. The preprotocrista is straight and terminates labially at the anterior end of paracone. The postprotocrista extends posterodorsally from the protocone and turns labially, ending dorsal to the posterior end of the metastylar lobe.

The M1 is transversely wider than P5 ( Fig. 3B ). Except for being larger, this tooth differs from M1s in Uchkudukodon nessovi in only a few details: the labial margin of the stylar shelf forms a more consistent ridge, the premetaconule crista is weaker (absent in the worn URBAC 02−91), and the metacingulum is wider. On the worn URBAC 02−91 there is a distinct parastylar groove. With wear, the preparaconule crista shifts its labial terminus posterolingually from the preparastyle to the anterior margin of the paracone. The parastylar lobe of the M1 of URBAC 02−91 is slightly more labial than in other M1s of this species. There are narrow but distinct pre− and postcingula on URBAC 02−91 but not on other M1s.

The M2 differs from M1 mostly in its more symmetrical stylar lobes, deeper ectoflexus, and relatively longer preparacrista. Compared with Uchkudukodon nessovi , M2s of D. inobservabilis appear to have more symmetrical stylar lobes, with a relatively less reduced metastylar lobe. URBAC 99−102 is an exception to this, with the parastylar lobe being distinctly larger than the metastylar lobe. This specimen also has a cusp−like preparacrista, which is not characteristic for other specimens.

In URBAC 00−43, an edentulous dentary, there are alveoli for the posterior root of p1, double−rooted p2, p4, dp5?, m1–2, and a hole for an unerupted m3. Judging from alveoli, p1–2, 4 gradually increased in size posteriorly. A long slit−like posterior mental foramen is under the alveoli for dp5?. In other specimens ( URBAC 00−55, 03−88, ZIN 88441), the posterior mental foramen is under the posterior root of p5.

Premolars anterior to p5 are not known, but the relative size of the p5 and alveoli for p 4 in ZIN 84972 suggest that p 5 in D. inobservabilis was shorter than p4, as in D. kulbeckensis and Uchkudukodon nessovi .

The p5 ( ZIN 84972, URBAC 03−88) ( Fig. 4 ) has a distinct paraconid, a broad but very short talonid with one posterior cusp (absent in ZIN 84972), and anterolingual and posterior cingulids. The talonid cusp in URBAC 03−88 is higher than the paraconid.

The m1–2s are generally similar in structure to lower molars of Uchkudukodon nessovi and Daulestes kulbeckensis . In URBAC 03−88 ( Fig. 4 ) the protocristid is set more obliquely than in other specimens. The cristid obliqua attaches slightly lingual to the protocristid notch in all molars.

Measurements.—See Tables 1 and 2.

Figures

Fig. 3. Stereopairs of Daulestes inobservabilis (Nessov, 1982); Dzharakuduk, Uzbekistan, Late Cretaceous (Turonian). A. URBAC 98−146, right P4 missing small part of anterior margin, in labial (A1) and occlusal (A2) views. B. URBAC 02−91, P5 and M1 from right maxilla with P5, M1, and alveoli for P4 and M2–3, in labial (B1), occlusal (B2), and lingual (B3) views. C. URBAC 98−140, left M2, in occlusal (C1), labial (C2), and anterior (C3) views.

Fig. 4. Stereopairs of Daulestes inobservabilis (Nessov, 1982); Dzharakuduk, Uzbekistan, Late Cretaceous (Turonian). URBAC 03−88, left dentary with p5, m1–3 (ventral margin is damaged and thus not shown); in labial (A), occlusal (B), and lingual (C) views.