Walshina, López-Torres & Silcox & Holroyd, 2018

López-Torres, Sergi, Silcox, Mary T. & Holroyd, Patricia A., 2018, New omomyoids (Euprimates, Mammalia) from the late Uintan of southern California, USA, and the question of the extinction of the Paromomyidae (Plesiadapiformes, Primates), Palaeontologia Electronica (37 A) 21 (3), pp. 1-28 : 6-7

Genus WALSHINA gen. nov.

Figures 4.1-4.4 , 5.1-5.11 , 6.1-6.19

zoobank.org/ 5F051939-CD72-4EBC-8BBC-3E6B637DC806

1968 Phenacolemur (Matthew, 1915) ; Robinson, p. 324

1976 Ignacius (Matthew and Granger, 1921) ; Bown and Rose, p. 112 (in part)

1978 Phenacolemur (Matthew, 1915) ; Krishtalka, p. 338, fig. 2-4

1990 Phenacolemur (Matthew, 1915) ; Mason, p. 2, fig. 2

1991a cf. Phenacolemur (Matthew, 1915) ; Walsh, p. 166, table 1

1996 Phenacolemur (Matthew, 1915) ; Walsh, p. 85, table 2

Type species. Walshina esmaraldensis gen. et sp.

nov.

Included species. Type species, Walshina

mcgrewi comb. nov. (= I. mcgrewi Robinson ,

1968), and Walshina shifrae comb. nov. (= Ph.

shifrae Krishtalka, 1978 ).

Distribution. Uintan and Duchesnean of Wyo-

ming, and Uintan of California.

Etymology. In memory of Stephen L. Walsh of the

San Diego Museum of Natural History, in recogni-

tion of his work on the San Diego County faunas.

Diagnosis. Paracristid of M 1 relatively long as in

Trogolemur and Sphacorhysis , but paraconid less

clearly distinct from the paracristid. Differs from Sphacorhysis (but not Trogolemur ) in having lower molar talonid basins that are relatively deep with smooth enamel. Differs from Trogolemur (but not Sphacorhysis ) in that the cristid obliqua of M 1 contacts the postvallid distal to the protoconid rather than between the protoconid and metaconid. Unlike the other trogolemurins, M 1 and M 2 of Walshina gen. nov. have strong hypoconulids with distinct foveae located below and buccal to the hypoconulid. As in Sphacorhysis , the distal aspect of M 1 and M 2 is convex, whereas in Trogolemur it is concave. M 3 hypoconulid narrower than in other trogolemurins. M 3 trigonid significantly taller than in Sphacorhysis (but not Trogolemur ). Like Sphacorhysis , lower molar entocristids form a rounded contour (i.e., forming a U-shaped entocristid) in lingual view, in contrast to the V-shaped entocristid in Trogolemur . Further differs from Trogolemur and Sphacorhysis in having much weaker buccal cingulids. Notably stronger precingulum on M 2 than in Trogolemur . Protocone lingual expansion on the upper molars not as pronounced as in Trogolemur . Compared to Trogolemur , mesial aspect of M 3 straighter, and the lingual border of that tooth much shorter mesiodistally relative to its buccal border.

Discussion. All trogolemurins share a distally expanded distolingual basin of the upper molars (particularly marked in W. mcgrewi comb. nov.), which is quite similar to that observed in paromomyid plesiadapiforms. This similarity is likely one reason why some members of Walshina gen. nov. have previously been considered paromomyids. However, in other ways the morphology of trogolemurins is inconsistent with that of paromomyids, including the presence of paraconids on M 3. Walshina gen. nov. remains quite poorly known, with the only record being isolated upper and lower molars. One likely reason for this limited record is that the genus includes the smallest North American omomyoids (see below).

Figures

FIGURE 4. Environmental SEM images of four teeth of Walshina esmaraldensis gen. et sp. nov. 1: left M3, SDSNH 76276; 2: right M1, SDSNH 76337; 3: right M2, SDSNH 76338; 4: right M3, SDSNH 72583. All teeth are in occlusal view. Arrow indicates the location of the fovea.

FIGURE 5. Photographs taken with digital camera (1, 4-11) and Micro-CT scan reconstructions generated using Avizo 7 (2, 3). Walshina shifrae comb. nov. (1, 4, 7, 10) – 1: right M1, CM 15797 (holotype; mirrored), in occlusal view; 4: left M2, CM 15103, in occlusal view; 7: left M, CM 21637, in occlusal view; 10: left M; CM 15726, in occlusal view. 2 3 Walshina esmaraldensis gen. et sp. nov. (2, 5) – 2: left M1, LACM 40198 (holotype), in occlusal view; 5: left M2, SDSNH 62850, in occlusal view. Walshina mcgrewi comb. nov. (3, 6, 8, 9, 11) – 3: left M1, CM 15635 (holotype), in occlusal view; 6: left M2, CM15794, in occlusal view; 8, 9, 11: left mandibular fragment with M, CM 29005, in occlusal 2 (8), buccal (9), and lingual (11) views.

FIGURE 6. Micro-CT scan reconstructions of specimens of Walshina esmaraldensis gen. et sp. nov. generated using Avizo 7: 1: left M1, LACM 40198 (holotype), in occlusal view; 2: left M2, SDSNH 87336, in occlusal view; 3: lingual fragment of a left M2, SDSNH 87337, in occlusal view; 4: lingual fragment of a right M2, SDSNH 42268, in occlusal view; 5, 6, 9, 10: left M2, SDSNH 87332, in occlusal (5), buccal (6), mesial (9) and lingual (10) views; 7, 8, 11, 12: mesial fragment of a left M1, SDSNH 87331, in occlusal (7), buccal (8), mesial (11) and lingual (12) views; 13, 14, 17, 18: left M3, SDSNH 87334, in buccal (13), occlusal (14), lingual (17) and mesial (18) views; 15, 16, 19: distal fragment of a right M3, SDSNH 87335, in buccal (15), occlusal (16) and lingual (19) views.