Oldfieldthomasia

MacPhee, R. D. E., 2014, The Serrialis Bone, Interparietals, “ X ” Elements, Entotympanics, And The Composition Of The Notoungulate Caudal Cranium, Bulletin of the American Museum of Natural History 2014 (384), pp. 1-69 : 1-69

Oldfieldthomasia (Unnamed Basal Typothere Group, Oldfieldthomasiidae )

Oldfieldthomasia has long been placed in its own family ( Simpson, 1967; Billet, 2011), to which a handful of other Paleogene taxa of debated affiliations (e.g., Acropithecus rigidus ) have gradually accreted, thus possibly rendering the family paraphyletic (see García López, 2011; Reguero and Prevosti, 2010; Billet, 2011). Available cranial material of this genus is decidedly poor, but retains historical importance because of Simpson’s (1936) study of Oldfieldthomasia cf. debilitata AMNH-VP 26800, discussed here in some detail (see figs. 1, 5–7, 20; appendix 1). This specimen is (or was) a partial skull from the locality of Cerro Blanco, now known to be of Middle Eocene age (cf. Reguero and Prevosti, 2010). Virtual sections of the preserved left

6 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 384

TABLE 1

List of Notoungulate Specimens

(E. = Early; Eoc. = Eocene; L. = Late; M. = Middle; Mioc. = Miocene; Pleist. = Pleistocene)

Institution Accession no. Genus Species Age Remarks a Scanned

TYPOTHERIA

[UNNAMED BASAL GROUP]

Oldfieldthomasiidae AMNH 28600 Oldfieldthomasia cf. debilitata M. Eoc. hemicranium, partial, left Y AMNH 28896 Oldfieldthomasia debilitata M. Eoc. skull, partial; poor

MACN 10376 Oldfieldthomasia debilitata M. Eoc. skull, poor (holotype)

INTERATHERIOIDEA

Interatheriidae

Interatheriinae AMNH 29651

MLP 2339

AMNH 29603

AMNH 9154

MACN A9857-58 MACN 9738-39

MLP 12—2780

MLP 26-IV-[?1]5-1

MLP 84-III-1-27

Notopithecinae AMNH 28949 AMNH 28673

Cochilius volvens L. Olig. –E. Mioc. skull, complete; excellent; Colhuehuapian

Cochilius volvens L. Olig. –E. Mioc. left auditory region only

(ex coll. Lillo); Colloncuran(?)

Progaleopithecus tournoueri L. Olig. –E. Mioc. partial skull in matrix, poor

(= Archeophylus), Scarritt Pocket, Deseadan

Interatherium robustum E. Mioc. skull

Interatherium robustum E. Mioc. auditory region, partial

Interatherium extensum E. Mioc. skull (= Icochilius extensus)

Protypotherium sp. E .–L. Mioc. skull, caudal portion, in matrix; periphery damaged, internally excellent; Santacrucian

Protypotherium sp. E .–L. Mioc. skull, caudal portion; fragmentary

Protypotherium sp. E .–L. Mioc. skull; significantly fractured

Notopithecus adapinus E.–M. Eoc. skull; poor; Casamayoran Notopithecus adapinus E.–M. Eoc. petrosal, isolated; poor;

Casamayoran

Y

Y

Y

Y

2014 MACPHEE: NOTOUNGULATE CAUDAL CRANIUM 7 8 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 384

hemicranium are of limited use because so much of the fossil has been lost or damaged (figs. 1, 7). Indeed, Simpson may have chosen this particular specimen to work on because it was already much battered and destructive sampling could be justified. This may have been the wrong choice for experimentation, however, for his results were predictably poor and he never attempted to prepare another South American ungulate in this manner.

OTHER SPECIMENS STUDIED. Also examined were the holotype skull of Oldfieldthomasia debilitata (MACN 10376) and another cranial specimen in the AMNH-VP collection (AMNH-VP 28896), but because of their condition (which Simpson [1932a: 7] unaccountably described as “well preserved”) they supplied nothing of value to the interpretation effort.