Sallamys quispea, Shockey & Gismondi & Gans & Jeong & Flynn, 2009

Shockey, Bruce J., Gismondi, Rodolfo Salas, Gans, Phillip, Jeong, Annie & Flynn, John J., 2009, Paleontology and Geochronology of the Deseadan (late Oligocene) of Moquegua, Perú, American Museum Novitates 3668, pp. 1-24 : 8-12

Sallamys quispea , sp. nov.

HOLOTYPE: MUSM 1404 , jaw fragment with lower right dp4-m1.

REFERRED SPECIMENS: Known only from the holotype.

TYPE LOCALITY: The upper Moquegua Formation, about 20 m below and southeast of the summit of Cerro Pan de Azúcar (fig. 1: d on the map).

ETYMOLOGY: The specific name, quispea , is given to honor Rossana Quispe of the city of Moquegua, who discovered the first fossils known from the Moquegua Formation. She also participated in all our field projects in the Moquegua Formation , during one of which she found the holotype of this diminutive rodent .

DIAGNOSIS: Smaller than all known Deseadan and Santa Rosa local fauna ( Perú) rodents, slightly smaller than the smallest known specimens of Sallamys pascuali ; brachydont; trilophate m1 with occlusal connection of the posterolophid to the hypololophid, mesolophid extending from the ectolophid; metalophid intersecting midpoint of anterolophid. The m1 anterolophid has a spur that with more wear would subdivide the fossetid into two. The m1 is subquadrangular, whereas dp4 is more ovoid. Molariform dp4; hypolophid with a small, posteriorly extending spur; anterolophid extends from protoconid around the anterior end of tooth to the metaconid, so that the anterolophid spur and metalophid tip join to form a figure eight– shaped fossetid.

DIFFERENTIAL DIAGNOSIS: Sallamys quispea differs from rodents of the Deseadan assemblage from Salla, Bolivia, in the following ways: It is most similar in overall morphology to Sallamys pascuali , but with lower crown height; dp4 not as molariform, but subequal in size to m1 (just 3% longer than m 1 in mesiodistal dimension), whereas dp4s of S. pascuali are larger (14%–25% longer than m1); anterior lophid of dp4 continuous from protoconid to metaconid, lacking the flexid that separates protoconid from anterior lophid of S. pascuali and lacking a second mesiolabial flexid; mesolophid of dp4 without connection to metaconid; less pronounced recurvature of lingual extreme of posterolophid of dp4 and m1; posterior spur at hypolophid-ectolophid junction of m1 shorter. Dental dimensions smaller than those of S. pascuali (mesiodistal dimension of dp4 just 82% that of smallest dp4 of S. pascuali and m1 mesiodistal dimension similar to that of only the smallest of individual sampled of S. pascuali , but with transverse dimension short- er than all). Differs from Branisamys luribayensis in its much smaller size (m1 mesiodistal dimension just a third of that of B. luribayensis ); m1 having only three major lophids, mesolophid not distinct or fully formed. Differs from Incamys bolivianus in smaller size (linear dimensions 40%–65% of those of Incamys ); labial hypolophid and posteriorlophid of m1 closer, forming a united crest with little wear (persistently separated in Incamys ); lingual spurs projecting from anterolophid of m1 with formation of an anterofossetid. Differs from Migraveramus beatus in having only three major lophids (mesolophid short, not reaching the metaconid), wider meta- and mesoflexids, and considerably smaller size (m1 mesiodistal dimension less than 75% to those of M. beatus ).

Sallamys quispea differs from rodents of the Deseadan of Patagonia: Differs from Platypittamys in more complex anterolophid, two anterofossetids. Differs from Deseadomys aram-

TABLE 2 Measures (mm) of the dp4 and m1 of Holotype (MUSM 1404) of Sallamys quispea sp. nov. of Moquegua, Perú, Compared to Those of Sallamys pascuali of Salla, Bolivia Data of Yale Peabody (PU) specimens are from Patterson and Wood, 1982.

bourgi by hypolophid more parallel to borders of occlusal surface and having additional anterofossetid. Differs from Deseadomys loomisi by presence of mesoslophid and semblance of metalophid. Differs from Scotamys by complexity of lobes and lack of cementum. Differs from Cephalomys by short hypoflexid, longer metaflexid and mesoflexid, brachydonty. Differs from Asteromys punctus by its much lower crown height, shallower flexids, and its much smaller size.

Differs from all known Santa Rosa local fauna rodents ( Eosallamys , Eoespina , Eodelphomys , Eoincamys , Eobranisamys , Eopicure , Eopululo , Eosachacui ) by m1 lacking a third fossetid of nearly equal length and depth, a feature characteristic of all members of the ‘‘Santa Rosa local fauna’’ rodent assemblage ( Frailey and Campbell, 2004).

DESCRIPTION: Among Deseadan rodents (and those from the uncertain age Santa Rosa local fauna), Sallamys quispea is closest in size and morphology to Sallamys pascuali , falling just below the lowest part of the size range of dental measures of specimens of S. pascuali from Salla (see table 2 and differential diagnosis above). Our study of a sample of small rodents from Salla referred to S. pascuali illustrates that that species is quite variable morphologically (assuming that all of these teeth indeed pertain to a single species). One dp4 (PU 20909; fig. 6B; see also Patterson and Wood, 1982: fig. 5d) has a discontinuous anterolophid separated from the protoconid by a flexid and further divided by an anterolabial flexid near the mesial apex of the tooth. Unlike that of S. quispea , the anterolophid connects to the mesolophid in the Bolivian specimens (PU 20909 and in UF 14458). The UF specimen, however, lacks the anterolabial flexid near the mesial apex as occurs on PU 20909. The wear pattern in both morphs is similar to that of the new Moquegua species of Sallamys in which the labial side wears more quickly than the lingual in both m1 and dp4. The mesiolingual end of the m1 of the Salla and Moquegua specimens have an ‘‘E’’ formation, made up of the tip of the anterolophid, a spur, and a short metalophid. In Sallamys quispea , however, the tip of the anterolophid joins with the metalophid rather than with the spur.

The m1 of Sallamys quispea has a distinct, but short, mesostylid, as does UF114759 (absent in PU 20909), but the m1 of the new taxon still is more complex in the anterior end of the molar than in the comparative specimens of Salla. The posterior side of the hypolophid is undulating in the new species. It is unlikely that S. quispea , at the same wear stage, would resemble UF 114759 and maintain a similar depth in its flexids (as in UF 114759).

COMMENT: Patterson and Wood (1982) considered the flexids of the dp4 of diagnostic significance for the genus Sallamys ; that is, species of Sallamys should be recognizable by the presence of two labial, one mesiolabial, and two lingual flexids. The absence of the mesiolabial flexid in at least one Salla specimen of Sallamys (UF 114458) and in S. quispea (which also lacks the labial flexid between the protoconid and anterolophid) indicates that the flexid number of the dp4 is an unreliable means of recognizing the genus Sallamys and apparently even the species S. pascuali .

ORDER LITOPTERNA AMEGHINO, 1889

FAMILY MACRAUCHENIIDAE GERVAIS, 1855

Genus and Species Indeterminate (cf. Coniopternium sp. )

Figure 4C, D

MATERIAL: MUSM 669, edentulous and damaged left mandibular ramus and right cuboid, found in slump below the conglomerates that form the base of the upper Moquegua Formation at the western flanks of Cerro Pan de Azúcar; MUSM 349, distal metapodial from the eastern summit of Cerro Mono.

COMMENTS: The metapodial (fig. 4C) is asymmetric and has a strong keel, thus representing one of the supportive metapodials (Mc II or IV; or Mt II or IV). Its distal keel is well developed, especially on the plantar surface where it is tall and bladelike. Unlike metapodal IIIs of macraucheniids ( Loomis, 1914: fig. 10; Shockey, 1999) the keel extends to the dorsal surface; however, it does not rise as high as that on the plantar side. The distal width is 18.2 mm, which is about the size of a similar element from Salla, cf. Coniopternium sp. (UF 173216), which has a distal width of 19.4 mm.

The cuboid (fig. 4D) is similar to that of Coniopternium andinum described and figured by Loomis (5 Notodiaphorus crassus of Loomis, 1914: fig.12). The apex of our specimen is damaged, thus obscuring any astragalar facet as noted by Loomis (1914) and Shockey (1999) for Coniopternium . The Mt IV facet is 17.0 mm wide and 21.1 mm deep. In distal view it is pear shaped, with the apex directed to the plantar side and widest dimension near the dorsal surface.

As known so far, the macraucheniid of Moquegua is not distinct from comparable material representing Coniopternium spp. from Salla, but it is too small to be referred to the Patagonian species, C. andinum . Unfortunately, diagnostic elements for Coniopternium , such as dentitions or the calcaneum, are lacking, so we must remain uncertain as to even the generic taxonomic reference of the macraucheniid of Moquegua.

ORDER NOTOUNGULATA ROTH, 1903

SUBORDER TOXODONTIA OWEN, 1853

FAMILY (PARAPHYLETIC) NOTOHIPPIDAE AMEGHINO, 1894

Figures

Fig. 4. Miscellaneous postcranial elements. A, phorusrhacoid claw (MUSM 351), in lateral and plantar views; B, dasypodid osteoderm (MUSM 1604) from the articulating region of the carapace; C, macraucheniid metapodial (MUSM 349) in dorsal, lateral, and plantar views; and D, right cuboid (MUSM 669) in dorsal and medial views.