Odontoceti, Flower, 1867

Boessenecker, Robert W., 2013, A new marine vertebrate assemblage from the Late Neogene Purisima Formation in Central California, part II: Pinnipeds and Cetaceans, Geodiversitas 35 (4), pp. 815-940 : 871-872

Odontoceti gen. et sp. indet.

REFERRED MATERIAL. — UCMP 219175, one partial left humerus collected by R.W. Boessenecker from UCMP locality V99854 .

STRATIGRAPHIC OCCURRENCE. — Lowermost part of the San Gregorio section of the Purisima Formation, latest Miocene (6.4-5.6 Ma; Messinian equivalent; Fig. 2 ).

DESCRIPTION

Ŋe partial humerus (UCMP 219175) is missing the distal end, and is slightly transversely crushed ( Fig.31 ). UCMP 219175 is tentatively identified as a left humerus, and is relatively large for an odontocete.Ŋe humeral head is large and oval in articular aspect, and was possibly circular prior to diagenetic compaction. Ŋe lesser tubercle is anteroposteriorly broad and oval-shaped in proximal aspect.An anteromedially oriented crest occurs on the proximal end, connecting the humeral head and the lesser tubercle. Ŋe humeral head is narrower than the lesser tuber- cle, and is oriented dorsomedially ( Fig. 31 ). UCMP 219175 appears to lack a greater tubercle.

REMARKS AND COMPARISONS

Ŋis specimen (UCMP 219175) differs from all fossil and modern phocoenids and many non-globicephaline delphinids(except Tursiops Gervais, 1855 ) in its larger size;although a humerus is not yet known for Parapontoporia Barnes,1984 , this specimen is almost certainly too large to belong to it. UCMP 219175 is similar in size and morphology to Albireo whistleri Barnes, 1984 . Ŋis specimen differs from kogiid humeri in lacking a prominent deltopectoral crest, and by having a lesser tubercle that is wider than the humeral head ( Kazár &Bohaska 2008).UCMP 219175differs from pontoporiids in its much larger size and exhibiting a transversely wider lesser tubercle ( Kazár & Bohaska 2008).Ŋis specimen differs from larger physeteroids in lacking a proximally small lesser tubercle and having a relatively thinner shaft ( Kazár & Bohaska 2008); it is not a ziphiid because of its possession of a larger and more prominent lesser tubercle. Ŋis specimen further differs from non-globicephaline delphinids in having a more elongate shaft ( Kazár & Bohaska 2008). Because this specimen is similar to both the monodontid Delphinapterus Lacépède, 1804 , Albireo Barnes, 1984 , and globicephaline delphinids, it is not identified to a more exclusive clade.

Figures

FIG. 2. — Stratigraphy of the Purisima Formation: A, Stratigraphic column of the San Gregorio section of the Purisima Formation (in meters), showing stratigraphic position of UCMP vertebrate localities, dated ash beds, diatom floras, and species of Carcharodon; thickness measurements start over above missing section in uppermost part due lack of overlapping strata; epoch and stage boundaries marked as "?" are estimated; modified from Boessenecker (2011a); Pliocene-Pleistocene boundary after Hilgen et al. (2012); B, photograph of 3-4 m thick ash within Purisima Formation at mouth of San Gregorio Creek correlated with 2.5 Ma Ishi Tuff (Powell et al.2007); C, trace fossils in pervasively bioturbated sandstone,Purisima Formation,mouth of San Gregorio Creek; D, swaley cross-stratified sandstone, mouth of San Gregorio Creek. Abbreviations: Qt, Pleistocene terrace deposits; Tp, Purisima Formation; C, claystone; St, siltstone; Ss, sandstone. Scale bars: A, 2 m; B, C, 10 cm.

FIG. 31. — Partial humerus of Odontoceti gen. et sp. indet.: A, UCMP 219175, anterior or posterior view; B, UCMP 219175 in medial view; C, UCMP 219175 in anterior or posterior view. Scale bar: 3 cm.