Nesophontes hemicingulus, Morgan & Macphee & Woods & Turvey, 2019

Morgan, Gary S., Macphee, Ross D. E., Woods, Roseina & Turvey, Samuel T., 2019, Late Quaternary Fossil Mammals From The Cayman Islands, West Indies, Bulletin of the American Museum of Natural History 2019 (428), pp. 1-81 : 13-14

Nesophontes hemicingulus , new species

Figures 3–9

HOLOTYPE: UF 23295 , partial skull lacking neurocranium (fig. 3); C1–M3 present on right side, C1–M2 on left side, with partial alveoli for I2–I3. Unfortunately, the skull broke along its long axis after collection, although little bone has been lost from complementary edges. All the cranial specimens from the Cayman Islands are damaged to a greater or lesser degree, and dentitions tend to be incomplete and much worn. UF 23295 was chosen as the holotype because its teeth are on average less worn than those in comparable specimens and all cheekteeth are preserved (albeit on one side only).

TYPE LOCALITY: Patton’s Fissure, near Spot Bay on the northern coast of Cayman Brac. The holotype was recovered from layer 5 (80–100 cm below the surface), which has been radiocarbon dated on the basis of land snail shell carbonate to 11,180 ± 105 14 C yr BP (see Radiocarbon Dating).

ETYMOLOGY: Frp, Latin hemi-, “half,” and cingulus, “belt,” in reference to absence of the precingulum on all upper molars.

AGE: Late Pleistocene-Holocene (see Radiocarbon Dating).

DISTRIBUTION: Known only from Cayman Brac and Grand Cayman. This species is the only member of the genus known outside the Greater Antilles and their satellite islands.

REFERRED SPECIMENS: Cayman Brac: Patton’s Fissure: partial skulls, UF 23258, 23264, 23277, 23279, 23293–23301, 23332–23337, 23360- 23363, 23393, 23394, 23407; mandibles, UF 23241, 23242, 23245, 23251–23256, 23259, 23265–23269, 23280–23285, 23311–23313, 23324–23326, 23343, 23347–23359, 23364, 23365, 23367–23378, 23383, 23389, 23397, 23398, 23400, 23404, 23408–23417, 23421, 23426–23432, 23436, 23437, 23448–23450 (also includes a large sample of postcranial material not listed here). Pollard Bay Cave, Shearwater Cave 2. Grand Cayman: Dolphin Cave: UF 172845 , right mandible with c1–m3; UF 172846 , right mandible with c1–m3; UF 172863 , right mandible with p2–m3; UF 172908 , left mandible with p2, p4–m3; UF 172909 , left mandible with c1, p2, m1–m3; UF 172910 , left mandible with m1–m3; UF 172926 , right mandible with m1– m2; UF 172939 , partial skull lacking braincase, with right C1–M2 and left P2-M2; UF 172940 , left mandible with p2, p4–m3; UF 172950 , left mandible m1–m2. Barn Owl Cave: UF 23242, right mandible with p2–m3. Bodden Cave: UF 23241, right mandible with p4–m3. Furtherland Farms: UF 172803 , left mandible with p2, p4– m3. Old Man Cave: UF 23245, right mandible with c1, p2, m1; UF 23246, right mandible with p2, p4–m3; UF 23247, edentulous right mandible; UF 23248, partial edentulous right mandible; UF 23249, right mandible with p2, p 4m 3; UF 23250, left mandible with p2, p4–m3; UF 23251, left mandible with p4–m3.

DIAGNOSIS: Within Nesophontes , N. hemicingulus expresses unique reductions in cingulum/ ectocingulid features on upper/lower molars. It can be distinguished in lacking precingula on all molars, attenuation of postcingula on M1 and M2, and uniform de-emphasis of ectocingulids on lower cheekteeth. Closest morphological similarities are to Cuban N. micrus in regard to tooth shape, dimensions, and discrete characters.

DESCRIPTION: In the absence of good cranial remains of Cayman nesophontids, teeth are the main source of characters (figs. 3–9). In the following set of differential diagnoses, we compare N. hemicingulus to species from the major islands on which Nesophontes formerly occurred: Puerto Rico ( N. edithae ), Cuba ( N. major , N. micrus ), and Hispaniola ( N. hypomicrus , N. paramicrus , N. zamicrus ). Hispaniolan N. paramicrus and Cuban N. micrus are very similar, and were in fact synonymized by Varona (1974) on the basis of his comparisons and those of Patterson (1962). However, these two species differ in some characters, such as the absence of a constricted infraorbital foramen in N. micrus , and for this reason are distinguished here. Cingulum/cingulid characters, the only reliably diagnostic characters for N. hemicingulus in the current hypodigm, are treated separately.

Figures

FIG. 3. Skull, Nesophontes hemicingulus, n. sp., UF 23295, holotype (Patton’s Fissure, Cayman Brac): A, right lateral; B, left lateral; C, occlusal (stereopair). Teeth moderately worn.

FIG. 4. Skull, Nesophontes hemicingulus UF 172939 (Dolphin Cave, Grand Cayman): A, right lateral; B, occlusal (stereopair). M3 missing on both sides; left M2 fractured.

FIG. 5. Skull, Nesophontes hemicingulus UF 23296 (Patton’s Fissure, Cayman Brac): A, left lateral; B, occlusal (stereopair). Teeth heavily worn; left M3 missing.

FIG. 6. Maxillary cheekteeth comparison, oblique lingual view: A, Nesophontes edithae AMNH 17109 (Cueva Catedral, Morovis, Puerto Rico); B, N. micrus (= N. longirostris) AMNH 17626 (Cave near Daiquiri, Cuba); C, N. hemicingulus UF 23295, holotype (Patton’s Fissure, Cayman Brac).

FIG. 7. Diagrammatic presentation of species variation in pre- and postcingula, based on various specimens: A, Nesophontes edithae; B, N. micrus; C, N. hemicingulus. In A, pre- and postcingula are developed on all molars; third molar occasionally expresses a lingual cingulum. In B, precingulum is absent on M2, postcingulum strongly reduced on M2 and absent on M3. In C, precingulum absent on all molars, postcingulum strongly reduced on M2 and absent on M3.

FIG. 8. Mandibular cheekteeth comparison, buccal and occlusal views (above and on successive pages): A, B, Nesophontes edithae AMNH 55005 (Cueva Catedral, Morovis, Puerto Rico); C, D, N. micrus AMNH 95708 (Cueva de los Macha [sic], Soledad, Cuba); E, F, N. hemicingulus UF 23252 (Patton’s Fissure, Cayman Brac).

FIG. 9. Diagrammatic presentation of species variation in ectocingulid definition, based on various specimens: A, Nesophontes edithae; B, N. micrus; C, N. hemicingulus.