Dsungarodon zuoi, Pfretzschner & Martin & Maisch & Matzke & Sun, 2005
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publication ID |
https://doi.org/ 10.5281/zenodo.13625285 |
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persistent identifier |
https://treatment.plazi.org/id/039C8792-A907-BA6F-F623-FE7202DCFC0F |
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treatment provided by |
Felipe |
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scientific name |
Dsungarodon zuoi |
| status |
sp. nov. |
Dsungarodon zuoi , sp. nov. Pfretzschner and Martin
Figs. 1–3 View Fig .
Derivation of the name: The species in named in honour of Prof. Zuo Xue−Yi, head of the Information Division of the Geological Bureau of Xinjiang in Urumqi,at the time director of the Xinjiang Geological Survey No. 1, for his long−term support of our fieldwork in the Junggar Basin .
Holotype: SGP 21, a right lower molar (L = 1.49 mm; W = 0.95 mm) ( Fig. 3A View Fig ).
Attributed material. SGP 23, a right upper molar (L* = 1.34 mm; W* = 1.58 mm) ( Fig. 2A); SGP 24, a fragmentary left lower deciduous premolar (L* = 1.09 mm; W* = 0.71 mm) ( Fig. 2B); SGP 25, a fragmentary left lower deciduous premolar (L* = 0.79 mm; W* = 0.79 mm) ( Fig. 2C); SGP 26, a right lower premolar (L = 0.76 mm; W = 0.38 mm) ( Fig. 3C View Fig ); SGP 22, a right lower molar (L = 1.28 mm; W = 0.87 mm) ( Fig. 2B).
Diagnosis.—As for the genus.
Description
Upper molar.—Specimen SGP 23 ( Fig. 2A) is a right upper molar probably from a middle position in the tooth row. Four cusps can be identified. On the buccal side of the tooth two cusps, A and C, are preserved. Cusp B is broken off. Of the two remaining buccal cusps the mesial cusp A is slightly higher than the more distal cusp C. The lingual projection of the triangular tooth crown bears two cusps, a large cusp X and a smaller cusp Y. All cusps are convex on their lingual side and concave on the buccal flank. On the concave buccal flanks of cusps A and C a smooth vertical ridge is developed.
Cusp A is slender and of conical shape. Its tip is slightly bent towards the buccal side and is worn. On the mesial side of cusp A, a well developed crest runs in a mesio−buccal direction where the broken cusp B was located. On the distal side of cusp A a crest descends into the deep notch between cusps A and C. Both crests bear well developed wear facets that are facing lingually. A third crest originates at the lingual base of cusp A and connects it with cusp X. This crest does not exhibit any wear facets but has a knotty edge.
Cusp C is bucco−lingually slightly compressed. As in cusp A, its tip is bent towards the buccal side, but is not worn. A crest that runs down its mesial flank bears along its entire length a well developed wear facet, inclined towards the lingual side. In occlusal view the crests between cusps A and C form an obtuse angle that points lingually. The wear facets of the two crests are not fused. On the distal flank of cusp C a disto−buccal crest also has a well developed lingually inclined wear facet over its entire length. The wear facet exhibits a faint striation in a bucco−lingual direction. All four buccal crests of cusps A and C form a continuous cutting edge.
Cusp X is strongly bent to the buccal side and has a hook−like appearance. Its tip bears a steeply inclined wear facet that faces in buccal direction. On the mesial side of cusp X, a crest originates at its tip and bends soon in buccal direction to meet the lingual crest of cusp A. The two crests form the mesial border of a basin. At the distal side of cusp X, a second crest connects cusp X with cusp Y. On the distal side of cusp Y, a crest runs in buccal direction. It does not meet cusp C, but continues as a distal cingulum at the base of cusp C. The distalmost part of the cingulum is broken off.
One striking feature of the upper molar is the wide buccal shelf with a strongly developed ectoflexus. The mesial corner of this shelf is broken off. The shelf forms a shallow trough which is bordered by a sharp rim.
At the mesial base of cusp X, a well developed mesial cingulum originates which runs buccally and probably met the buccal shelf at the bucco−mesial corner of the tooth; now parts of the cingulum are broken off.
The buccal flange of cusp X is steeply inclined and forms the lingual border of the basin. Both the mesial and the distal borders of the basin are deeply notched. Buccally the basin is bordered by the tall cusps A and C. These buccal cusps are twice as high as cusp X.
Lower deciduous premolars.—Both lower deciduous premolars ( Fig. 2B, C) are fragmentary and are from the left side. The teeth are molariform but differ from permanent lower molars by being laterally more compressed and mesio−distally elongated. In the more complete specimen SGP 24 cusps a, b, and c are preserved. Cusp a is the largest and bears three crests, crest a−c, crest a−b and a distal crest. Its tip is strongly worn and the dentine core is exposed. Cusp c has a recurved tip that is slightly worn and is connected to cusp a by crest a−c. Cusp b forms the mesial portion of the tooth. Besides crest b−a, a second crest originates at the mesial side of cusp b. It runs in mesial direction and meets a prominent mesio−lingual ledge at the mesial end of the tooth. The tip of cusp b is worn and the dentine is exposed. As there is neither a cusp g developed nor a crest connecting cusp b and c there is no basin present on the tooth crown.
The second specimen SGP 25 is a fragment with only cusps a and c preserved. Both cusps are strongly worn with the dentine exposed. The morphology of the tooth fragment corresponds in all details with the more complete specimen.
Lower premolar.—The right lower premolar SGP 26 ( Fig. 3C View Fig ) is double rooted with the anterior root broken off. Its crown is laterally compressed and the triangular main cusp is slightly recurved and has a small linguo−distally oriented wear facet on its tip. A crest runs down on its distal side and ends half way down. A small notch separates this crest from a small cuspule on the distal side of the main cusp. Distal to this cuspule a second crest continues the cutting edge and ends in a small enamel tip on the distal ledge. This ledge extends far anteriorly at the base of the lingual side. However, the most mesial part of the tooth is broken off together with the anterior root. On the buccal side a cingulum is developed that fades in the middle of the tooth crown.
Lower molars.—The holotype SGP 21 is a right lower molar preserved in a fragment of the mandible ( Fig. 3A View Fig ). Its position cannot be determined precisely, but it is definitely not the last of the tooth row as is evident from the presence of a partially preserved alveolus distal to it. The tooth is double rooted and is slightly wider than the preserved madibular fragment. The crown bears five cusps that can be identified as a, b, c, d, and g. Cusps e and f are not developed as distinct cusps.
The tooth crown is dominated by large cusp a, of which the upper portion is broken off. Cusp a is located disto−buccally and at its base four crests can be identified. A short crest runs on its mesial side towards cusp b. It has a well developed wear facet on the buccal side. A second crest without wear facets is located on the mesio−lingual side connecting cusps a and g. Crest a−c is only weakly developed and fades at the base of cusp c; it does not exhibit any wear facets. At the distal side a crest runs obliquely in lingual direction and stops at the base of cusp c.
The second highest cusp is cusp b which is situated in the mesio−buccal corner of the tooth crown. Three crests, a−b, b−g, and a mesial crest run down from the blunt apex of cusp b which is worn. Crest b−g is well developed and forms the mesial border of the anterior basin between cusps a, b, and g, corresponding to the situation in Simpsonodon and Krusatodon . The mesial crest runs slightly curved to the mesio−lingual end of the crown where in other docodonts cusp e is situated. In SGP 21 no distinct cusp e is developed. Between the mesial crest and crest b−g a straight valley runs perpendicularly to the long axis of the tooth.
Cusp g is the lowest of the main cusps and forms part of the margin of the mesial basin (“pseudotalonid”). It sits in a lingual position and is connected by a crest to cusp a as well as to cusp b. The tip of cusp g is bluntly worn and next to it crest g−b bears an elongated, mesially facing wear facet.
Cusp c is slightly higher than cusp g and is located in the disto−lingual corner of the tooth; it bulges somewhat over the lingual margin of the crown. The tip of cusp c is slightly bent disto−buccally and is bluntly worn. Besides the already mentioned low crest a−c a second crest runs from the distal side of cusp c in a disto−buccal direction towards cusp d. Cusp d forms part of of a ledge around the disto−lingual corner of the tooth crown. In contrast to other docodonts, in Dsungarodon no distinct cusp f is developed in the disto−lingual corner. It is not clear whether the distal ledge originally extended to the buccal side since this area of the tooth is slightly damaged.
Lower molar SGP 22 ( Fig. 3B View Fig ) is almost completely preserved and is still sitting in a fragment of the dentary. In lingual aspect ( Fig. 3B 3 View Fig ), the dentary exhibits the anteriormost part of the postdentary trough and the origin of Meckel's groove; the mandibular foramen is not preserved. SGP 22 is the last molar of the tooth row as is evident from the preserved base of the ascending coronoid process. The tooth exhibits a simplified morphology as is characteristic for the ultimate molar ( Krusat 1980) and is double−rooted. It is considerably smaller than the holotype and some of the cusps are reduced. Only three cusps are present that can be identified as cusps a, b, and g. Cusp a forms the distal portion of the tooth crown and is somewhat reduced in size; therefore it is no longer the highest cusp. The region distal to this cusp is reduced to a narrow ledge. Two crests originate at cusp a and run respectively mesio−lingually (crest a−g) and mesio−buccally (crest a−b). The two crests form the V−shaped distal border of the basin a−b−g. Cusp b is the largest of these three cusps. Three crests extend from cusp b: a−b, b−g, and a crest that runs in a lingual direction along the mesial bor− der of the tooth crown (equivalent of crest b−e of the docodonts where cusp e is developed). As in the holotype, a straight valley lies between the mesial crest (“b−e”) and crest b−g, which is oriented transversely to the long axis of the tooth. Cusp g is the most lingually situated cusp on the tooth and bulges over the lingual border of the dentary. It is connected by two crests with cusps a and b .
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