Small archaeohyracids (Typotheria, Notoungulata) from Chubut Province, Argentina, and central Chile : implications for Trans-Andean temporal correlation

28 Pages·2003·1.6 MB·English

by  Reguero, Marcelo

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no.48
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Geology
NEW
SERIES, NO. 48
Small
Archaeohyracids (Typotheria,
from Chubut
Notoungulata) Province,
Argentina, and Central Chile:
Implications for Trans-Andean
Temporal Correlation
Marcelo Reguero
Darin A. Croft
John
J. Flynn
Andre R. Wyss
November 26, 2003
Publication 1526
PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY
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UNiVERSITY OF ILLINOIS
AT URBANA-CHAMPAIGN
GEOLOGY
FIELDIANA
Geology
NEW
SERIES, NO. 48
Small
Archaeohyracids (Typotheria,
from Chubut
Notoungulata) Province,
Argentina, and Central Chile:
Implications for Trans-Andean
Temporal Correlation
Marcelo Reguero Darin A. Croft
Departamento Cientifico de Paleontologia DepartmentofOrganismalBiology
de Vertebratos andAnatomy
Museo de La Plata The UniversityofChicago
Paseo del Bosque s/n 1027 East57th Street
1900 La Plata Chicago, Illinois 60637
Argentina U.S.A.
John J. Flynn Andre R. Wyss
Department ofGeology DepartmentofGeological Sciences
FieldMuseum ofNatural History University ofCalifornia, Santa Barbara
1400 South Lake Shore Drive Santa Barbara, California 93106
Chicago, Illinois 60605-2496 U.S.A.
U.S.A.
Accepted May 7, 2003
Published November 26, 2003
Publication 1526
PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY
© 2003 Field Museum of Natural History
ISSN 0096-2651
PRINTED IN THE UNITED STATES OF AMERICA
^^
(S£><-e^^
GEOLOGY
ilBRAir/
Table of Contents 4. Cast of right maxillary fragment collect-
ed by Santiago Roth from Canadon
Blanco and referred to Protarchaeo-
Abstract 1 hyrax minor (gen. et sp. nov.), MLP 52-
Introduction 1 XI-4-168a 11
Chilean Fauna 1 5. Cast and drawing of specimen from Tin-
Argentine Fauna 2 guiririca Fauna ofChile referred to Prot-
Abbreviations 2 archaeohyrax intermedium (gen. et sp.
Nomenclatural Note 2 nov.): paired dentaries, holotype,
Systematic Paleontology 3 SGOPV 3065 12
Protarchaeohyrax gracilis 3 6. Cast and drawing of specimen from Tin-
Protarchaeohyrax minor 9 guiririca Fauna ofChile referred to Prot-
Protarchaeohyrax intermedium 11 archaeohyrax intermedium (gen. et sp.
Temporal Correlation and Conclusions ... 15 nov.): paired dentary fragments, SGOPV
Acknowledgments 16 5007 13
Literature Cited 16
7. Cast and drawing of specimen from Tin-
guiririca Fauna ofChile referred to Prot-
archaeohyrax intermedium (gen. et sp.
nov.): partial palate, SGOPV 2998 14
List of Illustrations
Endpiece: Speculative reconstruction of an
indeterminate archaeohyracid
1. Casts of specimens referred to Protar-
chaeohyrax (gen. nov.) 4
2. Cast of specimen from Tinguiririca Fau-
na of Chile referred to Protarchaeo-
List of Tables
hyrax gracilis (gen. nov.): mandibular
fragment, SGOPV 2954 5
3. Cast and drawing of specimen from Tin-
guiririca Fauna ofChile referred to Prot- 1. Measurements of teeth of Protarchaeo-
archaeohyrax gracilis (gen. nov.): ros- hyrax gracilis, P. intermedium, and P.
trum, SGOPV 2982 6 10
ui

Small Archaeohyracids (Typotheria, Notoungulata)
from Chubut Province, Argentina, and Central Chile:
Implications for Trans-Andean Temporal Correlation
Marcelo Reguero Darin A. Croft
John J. Flynn Andre R. Wyss
Abstract
We describe small-bodied archaeohyracids of transitional Eocene-Oligocene age from Chu-
but, Argentina, including two from Santiago Roth's important but poorly known Canadon Blan-
co locality and two occurring in the Tinguiririca Fauna of the Andean Main Range of central
Chile. Three taxa are recognized. We refer specimens from both Patagonia and the central
Andes to one ofthese taxa, initially named Arachaeohyrax gracilis by Roth (1903) but receiv-
ing a new generic designation here. A diminutive form from Caiiadon Blanco and an inter-
mediate-sized form from Chile are each recognized as new species. These taxa help to clarify
the temporal correlation of lithostratigraphic units currently located on opposite sides of the
Andean divide, and aid in the recognition ofa biochronologic interval, the early Oligocene (to
possibly late Eocene)-aged Tinguirirican, interposed between the classical Mustersan and De-
seadan "ages" of the South American land mammal succession.
Introduction the dominantly volcanic and volcaniclastic Aban-
ico {— Coya-Machalf) Formation (see Charrier et
Archaeohyracids are among the most poorly al., 1996). Attaining a stratigraphic thickness of
known of South America's early Cenozoic mam- up to 2000-3000 m, the Abanico Formation rep-
mals. In view of the group's typical rarity else- resents the geographically most widespread lith-
where on the continent (apart from the Deseadan ostratigraphic unit on the western (Chilean) slope
of Bolivia), the abundance and diversity of ar- of the central Andean Main Range. The Tingui-
chaeohyracids in the transitional Eocene-Oligo- ririca Fauna, documenting a pre-Deseadan (South
cene-aged Tinguiririca Fauna of central Chile American Land Mammal "Age;" SALMA), post-
(Wyss et al., 1994) are remarkable. Equally note- Mustersan (SALMA) biochronologic interval
worthy is a previously poorly understood, roughly (Tinguirirican SALMA) recently added to the
co—ntemporaneous faunule from Chubut, Argenti- South American fossil mammal succession (Wyss
nk1a9n0o1w,Rno1tf9hr0'3os)m.CCaTanwnaoaddoosnmnalBBlllaaannrcccooh.aaeOosnhseyermwabaclsiadgperteav(xiRaooutashr,-e eo1tf99aCl6.;e,nFo1l9z9yo4ni;ncFemltyaanmln.m,a&2l00S3wf)ia,suhneiasrs,thd1ei9s9fc5iro;svteBrooefnddawesitetrhailie.ns,
ly undescribed, and the other occurs also in the this formation during the past decade (Flynn et
Tinguiririca Fauna; both are named or renamed al., 1995; Wyss et al., 1996; Charrier et al., 1997;
below.
Wyss et al., 1999). Radioisotopic determinations
place the age of the Tinguiririca Fauna at —31.5
Chilean Fauna Ma (see Flynn et al., 2003), based on directdating
of several fossiliferous horizons (see Charrier et
The Tinguiririca Fauna (Wyss et al., 1990, al., 1996; Flynn «& Wyss, 1999). TheTinguirirican
1994; Wyss, Flynn, et al., 1993) is derived from SALMA is certainly earliest Oligocene in age and
FIELDIANA: GEOLOGY, N.S., NO. 48, NOVEMBER 26, 2003, PP. 1-17
possibly quite short in duration (—31-33 Ma), but in Chile and elsewhere in Argentina have re-
may extend into the late Eocene (Flynn et al., vealed, however, that the bulk of the Cafiadon
2003). Blanco assemblage likely pertains to a single fau-
Among numerous taxonomic peculiarities, the na, approximately contemporaneous with the Tin-
Tinguiririca Fauna contains by far the most di- guiririca Fauna and Ameghino's "Astraponoteen
verse archaeohyracid fauna known to date (Wyss, plus superieur" horizon from the Gran Barranca
Norell, et al., 1993; Wyss et al., 1994; Croft, south of Lake Colhue Huapi (Wyss et al., 1994;
1998, 2000; Croft et al., 2003). Indeed, archaeo- Bond et al., 1996; Reguero, 1998).
hyracids, represented by at least six taxa, are a Among its archaeohyracids, the Canadon Blan-
dominant element of the Tinguiririca Fauna both co fauna includes two small forms, ofwhich only
in numerical abundance and in taxonomic diver- Archaeohyraxgracilis (whose subsequent nomen-
sity. Uncertainty about the number of taxa stems clatural history is discussedbelow) has previously
from the u—nknown association ofupper and lower been named (Roth, 1903). Herein we provide a
dentitions aproblem compounded by the similar new generic designation for this species; we also
size ofseveral ofthe taxa and the time-consuming place within this genus two new diminutive spe-
preparation of specimens from extraordinarily cies, one from Caiiadon Blanco and one from the
hard matrix. Tinguiririca Fauna.
Several archaeohyracids from the Tinguiririca
Fauna are referable to forms known from Argen-
tina (Wyss et al., 1994); many such references Abbreviations
could previously be made only informally, owing
to the tangled nomenclature ofmany ofthe forms APS, Astraponoteen plus superieur; MLP, Mu-
from Patagonia. Here we seek to update and sta- seo de La Plata; SGOPV, Museo Nacional de His-
bilize the nomenclature ofa small archaeohyracid toria Natural, Santiago, vertebrate paleontology
common to the Caiiadon Blanco and Tinguiririca collections; MACN, Museo Argentino de Cien-
faunas, and describe two new, closely related cias Naturales, "Bernardino Rivadavia"; SAL-
forms. The other archaeohyracids from the Tin- MA, South American Land Mammal "Age."
guiririca Fauna are described formally elsewhere
(Croft et al., 2003). A minimum ofthree archaeo-
hyracid skulls are known from the Tinguiririca Nomenclatural Note
Fauna (skulls of this group were previously lim-
ited to a single specimen ofArchaeohyrax pata- Because the early phase of study of South
gonicus from Argentina and undescribed speci- American fossil mammals produced a plethora of
mens from Salla, Bolivia). In addition, the Tin- dubiously founded names, "whoever thinks he
guiririca Fauna provides associated postcranial has discovered a new taxon in these faunas is eth-
and dental material for the group. ically obliged to consider the[ir] possible appli-
cability. . . ," even though these names may have
"no real meaning at present" (Simpson, 1967:
Argentine Fauna 189). Taxonomists revising these faunas therefore
face arecurringconundrum: Is itpreferable to sal-
The fossil assemblage from Caiiadon Blanco is vage "classic" names based on inadequate holo-
among the most enigmatic in the South American types, effectively "rehabilitating" such names by
land mammal succession. Collected by Roth, referring more clearly diagnosable material to
probably during 1897 and 1898, the locale them, or are we better served in marginalizing
(known to occur within Chubut Province) has not very poorly substantiated names by expressly de-
been relocateddefinitively. (A manuscriptin prep- clining to add to their hypodigms? Even if the
aration by one of us, M.R., seeks to clarify the second alternative is followed, as Simpson (1967:
locations ofSantiago Roth's collecting efforts, in- 189) lamented, "it is vexatious that there is no
cluding Canadon Blanco.) Roth's specimens from way tojettison the latter [names that are unlikely
Cafiadon Blanco were long considered to repre- ever to acquire any meaning or value] perma-
sent a temporally mixed assemblage, representing nently and thus clear up accumulated clutter in
the Casamayoran, Mustersan, and Deseadan SAL- this science." For reasons outlined below we fa-
MAs (Simpson, 1967; Patterson, unpublished vor proposing new names over resurrecting prob-
manuscript; Patterson et al., in prep.). Discoveries lematic older ones.
FIELDIANA: GEOLOGY
Systematic Paleontology therefore, only "gracilis" is based on reasonably
diagnosable material. Ongoing work (Reguero &
Mammalia Linnaeus, 1758 Cifelli, 1997; Croft et al., 2003; Patterson et al.,
Notoungulata Roth, 1903 in prep.) has shown that Deseadan SALMA ar-
Archaeohyracidae Ameghino, 1897 chaeohyracids form a distinct clade (from which
"gracilis" is excluded), members of which pre-
Protarchaeohyrax, gen. nov. occupy the nameArchaeohyrax. Forthesereasons
we propose a new genus, Protarchaeohyrax, to
Archaeohyrax Ameghino, 1897 (partim): 431- receive "grac—ilis."
432. Diagnosis "Significantly smaller than [Ar-
=
Bryanpattersonia Simpson, 1967 (partim): 113. chaeohyrax Bryapattersonia] nesodontoides"
lEohegetotherium Ameghino, 1901: 370; Simp- (Simpson, 1967: 114). More brachydont than Ar-
son 1967; 115-116, figs. 31a, b. chaeohyrax; labial fossettes of upper molars per-
— sist little into wear. Parastyle large, more promi-
Type Species P. gracilis {=Archaeohyrax nent, and situated further labially relative to para-
gracilis). — cone than in Archaeohyrax. Paracone well devel-
Comments Patterson (MS) and Simpson oped. Lingual sulcus on upper molars.
(1967) recognizedArchaeohyraxsulcidens andA. Prolongation of M3 ectoloph forms a posterior
gracilis as belonging to a genus distinct from but lobe. —
closely related to Bryanpattersonia (and also dis- Distribution Tinguiririca Fauna, Abanico
tinct from Archaeohyrax), although neither ever (= Coya-MachalQ Formation, Chile, of early Ol-
named it formally. Nonetheless, not having seen igocene (to possibly late Eocene) age, Tinguiriri-
Roth's material, Simpson (1967) elected to pro- can SALMA (Flynn et al., 2003); presumably the
visionally assign bothA. sulcidens andA. gracilis Sarmiento Formation, Chubut, Argentina (Roth,
to a single species of his newly erected genus 1903); Fray Bentos Formation, Uruguay (Reguero
Bryanpattersonia (B. sulcidens, which had prior- et al., 1995). The occurrence ofthe genus in Uru-
ity overgracilis), along with a second, clearlydis- guay represents a new species that will be de-
tinct species, B. nesodontoides (the genotypic spe- scribed elsewhere.
cies). Simpson's (1967) B. sulcidens thus has yet
to receive distinct generic recognition, an action
taken below. It merits note that M. T. Cabrera's Protarchaeohyrax gracilis
sketches of Roth's "A." gracilis type material (Figures 1-3)
(appearing as figures 29 and 30 in Simpson, 1967)
are not entirely accurate, thus bearing on assign- Archaeohyrax gracilis Roth, 1903: 22.
ment of that material. ^Archaeohyrax sulcidens Ameghino, 1902: 10.
Even though both Patterson (MS) and Simpson ^BryanpattersoniasulcidensAmegh'mo, 1902: 10;
(1967) argued for the synonymy ofArchaeohyrax Simpson, 1967: 113.
sulcidens and A. gracilis, one of us (Reguero, ^Eohegetotheriumpriscum Ameghino, 1901: 370;
1998) has recently shown that a name proposed Simpson 1967: 115-116, figs. 31a, b.
still earlier, Eohegetotherium priscum, placed by —
Ameghino (1901: 24) in the Hegetotheriidae, HoLOTYPE OF Archaeohyrax gracilis MLP
might represent the same taxon. Thus, if ''sulci- 12-1522, fragment of left maxilla bearing P1-M3
dens,'' ''gracilis,'" and "priscum'''' could indeed (Fig. lA), and MLP 12-1518 (Roth's No. 4978),
be shown to be synonyms, Eohegetotherium left mandibular fragment with pl-m2 (both spec-
would be the valid generic name. Unfortunately, imens probably of the same individual, but with
the types and hypodigms of "sulcidens'' and MLP 12-1522 becoming lectotype should this as-
"priscum" offer such scant basis for comparison sociation prove incorrect; Simpson, 1967) (Fig.
(see below) that assignment to various earlier IB). —
named archaeohyracid species (each inarguably LectotypeofA. sulcidens Based on Amegh-
distinct) cannot be excluded. The case for syn- ino's description, Simpson (1967: 113) selected
MACN MACN
onymy is thus based less on the unmistakable A-10906a (misprinted as 1096 by
morphologic similarity of these forms than on Simpson), a left ml measuring 6.5 by 3.6 mm^ as
there being so little to compare that they can't be lectotype. The lectotype is from a lot of 24 teeth,
shown to be different. Of these three names, 14 ofthem lowers, two ofwhich match Simpson's
REGUERO ET AL.: SMALL ARCHAEOHYRACIDS FROM ARGENTINA AND CHILE
m2; MACN A-10906d, right ml or m2; MACN
A-10906e, right ml or m2; MACN A-10906f, left
MACN
m3; A-10909, left m3. —
Lectotype of Eohegetotherivm priscum
MACN A-10988a, right Ml or 2.
Paralectotype of Eohegetotherium PR/s-
cum—MACN A-10988b, left Ml or 2, MACN
A-10988c, ri—ght Ml or 2.
Hypodigm The holotype of Archaeohyrax
gracilis and the following specimens: MLP 12-
1478, cranial fragment with alveoli for right II-
3, right C, Pl-2, P3 (broken), and P4-M3 (Fig.
MLP
IC); 12-1513a, left mandibular fragment
with p4-m3; MLP 12-1513b (Roth's No. 4893),
right mandibular fragment with p2-m3; MLP 12-
1539, left mandibular fragment with ml-3; MLP
52-XI-4-168 (Roth's No. 4894), left maxillary
fragment with dP2-4, Ml-2 (consisting of two
pieces with a very good contact); SGOPV 2954,
right mandibular fragment with pl-m3 and por-
tion ofleft mandibularramus bearing lingual sliv-
ers of posterior teeth (Fig. 2); and SGOPV 2982,
rostrum with left and right dC, PI, dP2-4, Ml-
2; the left successional canine can be seen emerg-
ing above its deciduous precursor, while on the
right side ofthe specimen P2-4 are visible in their
crypts, nestled above their precursors (Fig. 3).
(The first postcanine teeth in notoungulates are
generally unreplaced, leading to ambiguity over
their properdesignation. Are these retained decid-
uous teeth [dPl/dpl] or successional teeth that
erupt unusually early [Pl/pl]? Inasmuch as com-
Fig. 1. Epoxy casts ofspecimens collectedbyCarlos plete ontogenetic series are needed to decide this
Ameghino and Santiago Roth referred here to Protar- question in modern forms, it will likely never be
ci(lhiMsa,LePoinhcyl1ru2ad-xi1n5gg2ra2(c)iAl)iisnfr(oagcegcnml.eunsntaolv.o)f(.tloHepfo)tlomatanyxdpielsllaaobifwail"tAh.(b"Po1tg-traoMcm3-) cteonntclwuistihvetlhyertersaodlivtieodnaflordensoitgonuantgiuolna,tewse. iCdoennstiisf-y
views and (B) occlusal view ofleft mandibular fragment these teeth as—Pl/pl.)
with pl-m2 (MLP 12-1518). (C) Right maxillary frag- Localities The provenience of the lectotype
m(aelnvteolwiitfhorC1,1-PI3-n2o,tPv3isi(bblreokoenn)c,asPt)4.-SMc3ale(MbaLrP=121-01m47m8.) ofB. sulcidens is uncertain, Simpson (1967: 114)
simply indicating it to be from the Mustersan
(SALMA) ofPatagonia (see above, and Temporal
Correlation section below). Similarly, the locality
description. Of these two teeth (ml or possibly from which the lectotype of E. priscum (MACN
m2), we designate the one less encrusted in man- A-10988) derives is not known but is thought to
ganese and clearly showing the central fossette be in central Chubut Province. (MACN A-10988
between the trigonid and talonid as the lectotype. was found among the syntypes ofA. sulcidens; it
Among the various labels accompanying these was separated from this lot ofspecimens and giv-
teeth, one, apparently an annotation by B. Patter- en its present number during intervening work on
son, reads, '"Archaeohyrax sulcidens Ameghino the collections.)
... (2 niveles)." Anotherreads ''Eohegetotherium Specimens bearing Museo de La Plata numbers
priscum Tipo," and ''Astraponotus.'' — are part of Roth's collection from Caiiadon Blan-
Paralectotypes of a. sulcidens MACN co, the precise location of which is now lost (see
A-10906b, left ml; MACN A-10906c, left ml or above). Roth labeled these specimens "T.i.C.B."
FIELDIANA: GEOLOGY