Kimbetopsalis simmonsae, Williamson & Brusatte & Secord & Shelley, 2016
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https://doi.org/ 10.1111/zoj.12336 |
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https://treatment.plazi.org/id/03DB2D32-AE00-B875-3A49-29339769FAA3 |
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Marcus |
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scientific name |
Kimbetopsalis simmonsae |
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KIMBETOPSALIS SIMMONSAE GEN. ET SP. NOV.
( FIGS 1 View Figure 1 , 2 View Figure 2 , TABLES 1 AND 2) (http://zoobank.org/ urn:lsid:zoobank.org:pub:9E9F07C3-D042-4E8F-862A-279072E04035 )
Holotype
NMMNH P-69902 from locality L-9181.
Type locality and horizon
The specimen was discovered in the lower Palaeocene part of the Nacimiento Formation of the San Juan Basin of northwestern New Mexico, in the west flank of Kimbeto Wash, at locality 11 of Williamson (1996: fig. 18). It is from Fossil Horizon A and within the Hemithlaeus kowalevskianus – Taeniolabis taoensis Biozone (H-T Zone) ( Williamson, 1996). The vertebrate fauna from this horizon is considered part of the type faunas of the middle Puercan Interval Zone (Pu2) ( Archibald et al., 1987; Williamson, 1996; Lofgren et al., 2004).
The west flank of Kimbeto Wash has yielded numerous taxa that are restricted to the H-T Zone, including Hemithlaeus kowalevskianus and Conacodon entoconus . These taxa are particularly abundant in H-T Zone faunas of the Nacimiento Formation, but are absent from the overlying Fossil Horizon B that yields the type faunas of the late Puercan Interval Zone (Pu3) ( Williamson, 1996). Furthermore, no specimens of T. taoensis have been recovered from the west flank of Kimbeto Wash. This is important because the first occurrence of Taeniolabis defines the beginning of the Pu3 Interval Zone ( Archibald et al., 1987; Lofgren et al., 2004). Although it does not in itself support a Pu2 age for the locality, the absence of Taeniolabis is further evidence that the west flank of Kimbeto Wash is not Pu 3 in age (a time when other large taeniolabidids are known from the Nacimiento Formation). Specimen NMMNH P-69902 was found fragmented, but in close association, weathering from a silty mudstone in an area of low relief. There is no possibility that the specimen is float from a higher horizon and therefore we are confident that it is a member of the H-T Zone fauna, and thus is Pu 2 in age.
Etymology
Kimbeto, for Kimbeto Wash; psalis, ‘cutting shears’ (Greek). Simmonsae, after Nancy Simmons, in recognition of her work on taeniolabidoid multituberculates.
I2, second upper incisor; L, length; M, upper molar; P, upper premolar; W, width.
*estimated.
I2, second upper incisor; L, length; M, upper molar; m, lower molar; P, upper premolar; p, lower premolar; W, width. *estimated.
Diagnosis
Taeniolabidid taeniolabidoid multituberculate that is smaller than Taeniolabis (4% smaller than Taeniolabis lamberti ; ∼ 21% smaller than T. taoensis ), has fewer M1 cusps (eight cusps in the buccal and median rows of M1, compared with nine or more cusps in the buccal and medial rows in Taeniolabis ; Simmons, 1987), and has a larger P4/M1 ratio (0.47, compared with 0.40 in Taeniolabis ). It has a greater number of M2 cusps (1:4:5) than any species of taeniolabidoid other than Taeniolabis (outside of Taeniolabis , no taeniolabidoid has more than three cusps in the median cusp row of M2).
Possible additional specimens
Sloan (1981) referred an edentulous left dentary preserving two prominent alveoli from the Puercan of the San Juan Basin (AMNH 3030) to Catopsalis foliatus . This specimen was originally referred by Cope (1888b) to the eucosmodontid multituberculate Eucosmodon molestus , an identification that Granger & Simpson (1929: 651) considered to be incorrect because it was much larger and more robust than the ‘neotype’ of Eu. molestus . McKenna (1960) also found the affinities of this specimen ‘puzzling’ because he considered that the two preserved alveoli would not have housed a large, elongate, double-rooted premolar, nor were they likely to have housed a small, singlerooted premolar and the anterior root of the m1. Sloan (1981) argued that the size and proportions of the ramus were consistent with the size and proportions of Ca. foliatus . However, Lucas et al. (1997) argued that the dentary was much larger than that of Catopsalis fissidens , which is significantly larger than Ca. foliatus , and with an incisor width of 8.3 mm, based on alveolar diameter, was within the size range of T. taoensis . An alternative interpretation is that AMNH 3030 is a mandibular ramus of Ki. simmonsae , which is expected to be smaller than T. taoensis , but larger than Ca. fissidens , the next largest taeniolabidoid that has been previously documented from the Nacimiento Formation. Unfortunately, the dentary and dentition is unknown for Kimbetopsalis , making direct comparison between Kimbetopsalis and AMNH 3030 currently impossible. We hope that additional discoveries will clarify the systematic position of AMNH 3030.
Sloan (1981) referred a left lower incisor from fossil horizon B of De-na-zin Wash (USNM 23273) to Catopsalis utahensis (here considered a junior synonym of Ca. foliatus ; see below). He considered it much too large (maximum height = 8.0 mm; maximum width = 5.7 mm; ventral radius of curvature approximately 51 mm; Sloan, 1981) to belong to Ca. foliatus . It may be that this specimen belongs to Ki. simmonsae , a taxon unknown at the time of Sloan’s description, but because it lacks longitudinal fluting it probably does not represent a lower incisor of that taxon.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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