Pararyctes rutherfordi, S.Scott & C.Fox & P.Youzwyshyn, 2002

S. Scott, Craig, C. Fox, Richard & P. Youzwyshyn, Gordon, 2002, New earliest Tiffanian (late Paleocene) mammals from Cochrane 2, southwestern Alberta, Canada, Acta Palaeontologica Polonica 47 (4), pp. 691-704 : 698-699

Genus Pararyctes Van Valen, 1966 Pararyctes rutherfordi sp. nov.

Fig. 3A–C ; Table 4.

Holotype: UALVP 45094 , incomplete right maxilla with P4, M2–3, Fig. 3A 1 , A 2.

Type horizon and locality: Cochrane 2, Paskapoo Formation, southwestern Alberta.

Age and distribution: Earliest Tiffanian of Alberta (type locality) .

Etymology: Named after R.L. Rutherford, for his early work on the geology of the Cochrane region and his participation in the discovery of the Cochrane 2 locality.

Material.—UALVP 25180, M2; UALVP 25178, 25179, 45095, m1s or m2s.

Diagnosis.—Differs from P. pattersoni Van Valen, 1966 in much larger size (with molars approximately 40 percent larger than in P. pattersoni ), in having a relatively broader postcingulum on M2, and having more transverse lower molars.

Description.—P4: P4 is triangular in occlusal outline and three−rooted.The paracone dominates the crown and is labio − lingually compressed.The parastylar lobe is slightly dam − aged on the holotype, but projects strongly anteriorly from the base of the paracone.No metacone is developed.The metastyle is of similar morphology with respect to the parastyle, but more labiolingually compressed and extends posterolabial to the paracone.An ectocingulum is faintly de − veloped.The protocone is half the height of the paracone and subcrescentic in occlusal view; strong wear is present along the posterior face of the protocone and along the postcingulum.The preprotocrista is strongly developed, connect − ing the apex of the protocone to a point just below the parastylar lobe.

M2: These teeth are similar to M2, P. pattersoni , albeit substantially larger.The paracone and metacone are closely appressed, being connate at their bases.The protocone is large and projects anteriorly.The postmetaconule crista and postprotocrista form a long, uninterrupted crest along the posterior labiolingual margin of the crown.The pre− and postcingulum are both well developed; the postcingulum differs from that in P. pattersoni in being anteroposteriorly wider at its labial extent.

M3: M3 is strongly compressed anteroposteriorly, forming a scalene triangle in occlusal outline.The hook−like parastylar lobe is especially prominent, projecting anterolabially from the trigon and over the metastylar area of M2. No stylocone is developed; a large, somewhat worn parastylar cusp is positioned on the anterolabial corner of the parastylar lobe.The paracone is tall and spire−like, and is connected to the parastylar lobe by a weakly developed preparacrista.The metacone is low, about one−third the height of the paracone, and projects anteriorly.The centro − crista is shallow, with the paracone and metacone being joined at their bases.The metastylar lobe is reduced; as a re − sult, the ectoflexus is shallow, and the ectocingulum is poorly developed.The paraconule, although present, is weak and is located more lingually than the even weaker metaconule; the preparaconule crista is moderately developed, while the postmetaconule crista is absent.Although post−mortem abrasion has reduced the original proportions of the lingual face of the protocone, the cusp appears to have been low, about the same height as the metacone.The pre− and postprotocrista are moderately developed, and faint pre− and postcingulum are present.

m1 or m2: The lower molars of P. rutherfordi resemble teeth of P. pattersoni , but are proportionally much larger in size, longer, and wider.The paraconid is conical and medial in position; the metaconid and protoconid are nearly equal in size and height, and lean slightly posteriorly.The talonid is short and twisted labially; its cusps are tall and conical, and the talonid basin shallow.No entocristid is developed, leav − ing the talonid open lingually.

Remarks.— Van Valen (1966) based the genus Pararyctes on P. pattersoni from the early Tiffanian Saddle locality (Fort Union Formation, Bison Basin), Wyoming.From Russell’s (1932) fig.10, a probable right P4 of “ Diacodon ” septentrionalis, Van Valen (1966) correctly concluded that P. pattersoni was present at Cochrane 2, as well.The teeth of P. rutherfordi from Cochrane 2 are much larger than those of P. pattersoni ; they are also larger than the teeth of an undescribed new species of Pararyctes from the Torrejonian Diss locality, Alberta ( Fox 1983; Fox 1990), but smaller than those of a second undescribed new species of Pararyctes from the middle Tiffanian DW−2 locality, Alberta ( Fox 1990).

Figures

Fig.3. A–C. Pararyctes rutherfordi sp.nov., Cochrane 2 locality, Alberta. A.Holotype, incomplete right maxilla with P4, M2–3, UALVP 45094 in occlusal view (A1, A2). B.Left M2, UALVP 25180 in occlusal view. C.Left m1 or m2, UALVP 45095 in labial (C 1), lingual (C2), and occlusal (C3) views. D–I. Bessoecetor septentrionalis comb.nov., Cochrane 2 locality, Alberta. D.Right P4, UALVP 25119 in occlusal view. E.Left M1, UALVP 28423 in occlusal view. F.Left M2, UALVP 28412 in occlusal view. G.Right p4, UALVP 28438 in labial (G 1), lingual (G2), and occlusal (G3) views. H. Left m2, UALVP 28414 in labial (H1), lingual (H2), and occlusal (H3) views. I.Holotype, left m3, UALVP 126 in labial (I 1), lingual (I2), and occlusal (I3) views.Scale bars 1 mm.

Fig.1. A–C. Ptilodus gnomus sp.nov., Cochrane 2 locality, Alberta. A.Holotype, right P4, UALVP 45145 in labial (A 1), lingual (A2), and occlusal (A3) views. B.Left p4, UALVP 45148 in labial (B 1), lingual (B2), and anterior (B3) views. C.Incomplete left dentary having i1, p3–4, UALVP 18670 in labial (C1) and lingual (C2) views. D. Baiotomeusrusselli sp.nov., Cochrane 2 locality, Alberta.Holotype, left P4, UALVP 18787 in labial (D 1), lingual (D2), and occlusal (D3) views. E–H. Thryptacodonorthogonius, comb.nov., Cochrane 2 locality, Alberta. E.Left M1, UALVP 45099 in occlusal view. F.Holotype, left M2, UALVP 124 in occlusal view. G.Left M3, UALVP 24993 in occlusal view. H.Right m1, UALVP 42872 in labial (H 1), lingual (H2), and occlusal (H3) views. Scale bars 1 mm.