Neocnus Arredondo, 1961

R D E Macphee, Jennifer L White & Charles A Woods, 2000, New Megalonychid Sloths (Phyllophaga, Xenarthra) from the Quaternary of Hispaniola, American Museum Novitates 3303, pp. 1-32 : 13-15

Neocnus Arredondo, 1961

Neocnus is one of several Antillean sloth genera with a complicated systematic past,

5 Although Neocnus (Arredondo, 1961) has priority over Cubanocnus (Kretzoi, 1968) at the genus level (operation of ICZN art. 40 [a][i]), Cubanocnini (Varona, 1974) was the first suprageneric nomen given to this group. It therefore has priority at the tribal level.

which witnessed taxa being multiply synonymized and specimens being reassigned with apparent abandon. Here it is sufficient to note that Neocnus as currently constituted by White and MacPhee (in press) is a relatively large but logically bounded genus, with two species in Cuba ( N. major , N. [= Microcnus ] gliriformis) and three in Hispaniola (N. [= Synocnus ] comes 6, plus two new species diagnosed here). Ascertaining species limits in a group of highly variable but not necessarily well sampled taxa is challenging, and some of the Neocnus species listed here may require further systematic treatment. As a group, the outstanding features of neocnuses are their small body sizes and skeletal indications of great arboreal agility. Osteologically, it is of some interest that none of the Hispaniolan specimens was found with jugals attached; nor have any isolated jugals been recognized in the collections made thus far. Unlike other megalonychids, which exhibit a broad sutural attachment area for the jugal, Neocnus has an attachment area that is no more than a raised dimple or shallow pocket on the maxilla, suggesting that this element (and related masseteric musculature?) may have been highly reduced (see fig. 12).

DIAGNOSIS OF GENUS: Small body size; cranial flexion absent; postorbital constriction weak; mandibular caniniform grooved posterointernally; last mandibular molariform with deep lingual groove; femoral shaft anteroposteriorly flat and medially bowed with prong on anterior aspect (except for N. toupiti ; see below); fibular facet of astragalus truncated and crescent­shaped; humerus short and slender but with prominent and squared supracondylar ridge; pronator quadratus flange confined distally.

Neocnus dousman , new species HOLOTYPE: Skull ( UF 76363 ; fig. 7) without clear associations, found 21–22 September 1983 by D. Cordier and party.

6 Inclusion of Synocnus within Neocnus may seem controversial in that Synocnus is usually considered an ally of Acratocnus . However, this move is warranted because Paula Couto’s (1967) hypodigm is mixed (includes elements that actually belong to Parocnus ) and his taxon definition is therefore unworkable. Absent the Parocnus specimens, it is evident that the remaining hypodigm represents a species that is phylogenetically Neocnus , not Acratocnus (White and MacPhee, in press).

TYPE LOCALITY AND AGE: Trouing de la Scierie, Morne la Visite , Département del’Ouest, Haiti; late Quaternary (see appendix 1 for additional details) .

SYNONYMS: None.

REFERRED SPECIMENS: Hypodigm also includes a mandible (UF 76370; see fig. 8)

from the same locality and a number of postcranial elements from other localities (see fig. 11). From Trouing Deron #1, Plain Formon: right femur (UF 76204), right tibia (UF 170207), left humerus (UF 170105), left ulna (UF 170106), and right radius (UF 170107); from Trujin Bridge, Morne la Visite: right

Fig. 7.

femur (UF 76270/285), left humerus (UF 75575), left ulna (UF 75634), right astragalus (UF 170240), and right tibia (UF 75469); from Trouing Jérémie #5, Plain Formon: right calcaneus (UF 170291); from Trou Diable, St.­Michel: right calcaneus (UF 170205).

ETYMOLOGY: Haitian Creole adjective meaning ‘‘slow,’’ pronounced approximately [doos­manh]; reference is to the classic behavioral characteristic of sloths. Recommended common name: Lesser neocnus.

DISTRIBUTION: Haiti and Dominican Republic.

DIAGNOSIS OF NEW SPECIES: With regard to known elements, agrees with features that define the genus. Differs from other Neocnus species in having sagittal crest consistently present; cranium flattened; lateral groove of pterygoid present; symphyseal spout long, Continued.

narrow, and untapered (relative to N. comes ); proximal fibular facet of tibia oval, robust, and posteriorly oriented; femoral shaft with slight anterior prong; quadriceps femoris tubercle (= tibial tuberosity) forming hook with groove; pronator quadratus flange forming abrupt lateral crest; bicipital tuberosity anteriorly placed.

DISCUSSION: See next entry.