Novttates PUBLISHED by the AMERICAN MUSEUM of NATURAL HISTORY CENTRAL PARK WEST at 79TH STREET NEW YORK, N.Y

AMERICAN MUSEUM Novttates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET NEW YORK, N.Y. 10024 U.S.A. NUMBER 2694 FEBRUARY 25, 1980

LEONARD RADINSKY Endocasts of Amphicyonid Carnivorans

AMERICAN MUSEUM Norntates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 2694, pp. 1-11, figs. 1-6, table 1 February 25, 1980

Endocasts of Amphicyonid Carnivorans

LEONARD RADINSKY1

ABSTRACT Endocranial casts of 10 genera of amphicyo- sulcus between the caudal ends of the ectolateral nids, ranging in age from about 35 my to 10 my, and suprasylvian sulci, and a complete, unoper- reveal evolutionary trends of increase in relative cularized ectosylvian sulcus. The ectolateral sul- brain size and expansion and increased folding of cus is a derived character amphicyonids share the neocortex. Amphicyonids had a distinctive with canids, in contrast to a derived feature of pattern of cerebral convolutions, characterized by basicranial circulation that links amphicyonids to the presence of a long ectolateral sulcus, a short ursids.

INTRODUCTION The Amphicyonidae are an extinct family evolutionary trends, and to call attention to of carnivorans that lived during middle Ter- features that may help to assess the phylo- tiary time, from about 40 to 10 million years genetic relationships of the family. ago. Most amphicyonids were medium-sized to very large, and ranged in appearance from ACKNOWLEDGMENTS wolflike to bearlike. Some workers believed they were most closely related to the Cani- I thank Drs. R. Hunt, University of Ne- dae (e.g., Romer, 1966; Bonis, 1969), but the braska, and R. Tedford, the American Mu- most recent studies have stressed affinities seum of Natural History, for information and with the Ursidae (e.g., Hunt, 1977; Gins- advice on amphicyonids, and Dr. G. de burg, 1977). During the course of a survey of Beaumont, Museum d'Histoire Naturelle, carnivoran brain evolution, I prepared sev- Geneva, Switzerland, for a copy of the Pseu- eral new endocasts of amphicyonids that ex- docyonopsis ambiguus endocast. I am grate- tend our knowledge of the neuroanatomy of ful to the curators of fossil mammal collec- this group. The purpose of the present paper tions at the following institutions for is to review what is known about the external permission to study specimens in their neuroanatomy of amphicyonids, to describe charge: American Museum of Natural His-

1 Research Associate, Department of Vertebrate Paleontology, American Museum of Natural History; Professor of Anatomy, University of Chicago.

5 5

10 am phicyonine - 10

15 - Amnph/cyon PI/ocyon - 5 A mphicyon 20 - 20 Daphoenoodon

25 - Temnocyon Cyne/os (Ysengrin/a) - 25

30 - Daphoenus Bra chycyon _ 30

35 Daphoenus (Daphoenictis) Pseu docyonopsis - 35

40 - 40 FIG. 1. Temporal distribution of amphicyonid genera for which endocasts are known. Numbers at sides indicate millions of years ago. North American occurrences are at left; European at right. Paren- theses indicate genera for which only a little of the endocast is preserved. See text for more detailed taxonomy and stratigraphic information.

tory; Carnegie Museum, Pittsburgh; Field GEN, Museum d'Histoire Naturelle Museum of Natural History, Chicago; Uni- LY, Universite Claude Bernard versite Claude Bernard, Lyon; Museum of MCZ, Museum of Comparative Zoology Comparative Zoology, Harvard University; MNHN, Museum National d'Histoire Naturelle Museum National d'Histoire Naturelle, Par- PU, Princeton University is; Princeton University; and South Dakota SDSM, South Dakota School of Mines School of Mines, Rapid City. This work was supported by N.S.F. grant DEB76-17746. THE EVIDENCE EARLY AMPHICYONIDS: Amphicyonids The following institutional abbreviations appeared about 35 to 40 my in North Amer- are used: ica and Europe, and the oldest known am- AM, American Museum of Natural History phicyonid endocasts are from early to middle CM, Carnegie Museum Oligocene deposits (about 30 to 35 my) from F:AM, Frick American Mammals, Department of the European amphicyonines Pseudocyop- Vertebrate Paleontology, American Museum of sis and Brachycyon, and the North Amer- Natural History ican daphoenines Daphoenus and Daphoe- FMNH, Field Museum of Natural History nictis. Daphoenus is the best known of these 1980 RADINSKY: AMPHICYONID CARNIVORANS 3

2 Cm.

FIG. 2. Daphoenus hartshornianus. SDSM 51121, x1. Abbreviations: cl, coronolateral sulcus; ec, ectolateral sulcus; en, entolateral sulcus; fp, fissura prima; rh, rhinal fissure; ss, suprasylvian sulcus. genera, and is represented by several endo- imens, variably developed dimples under the casts, one of which was briefly described by suprasylvian sulcus that mark the beginnings Scott and Jepsen (1936). The specimen fig- of an ectosylvian sulcus. In one of the Da- ured by Edinger (1956, fig. 5) under the name phoenus endocasts (PU 12588), the ectosyl- Daphoenus (AM 6946) is an endocast of the vian sulcus is expressed as a complete arch, canid Mesocyon. the suprasylvian sulcus is longer and more The brain of Daphoenus (fig. 2) had three arched than in the other specimens, and the main neocortical sulci, a relatively straight rostral end of the coronolateral sulcus is coronolateral sulcus that paralleled the dor- bowed out laterally. There is not enough evi- sal midline, a gently arched suprasylvian sul- dence to indicate whether the more ad- cus that approximately paralleled the rhinal vanced condition of neocortical folding in fissure, and an ectolateral sulcus that in three this specimen represents a species-specific of the six specimens I examined extended difference, or merely one extreme of individ- rostrally to contact the suprasylvian sulcus. ual or intraspecific variation. The cerebellum In addition, there was a short, variably de- was widely exposed, and the configurations veloped entolateral or postlateral sulcus that of the vermis, with a sharply marked fissura is sometimes confluent with the caudal end prima, the ansiform lobules and the parafloc- of the coronolateral sulcus, a short sulcal culus are discernible on Daphoenus endo- notch in the caudal border of the temporal casts. lobe between the ends of the ectolateral and A partly exposed natural endocast of Da- suprasylvian sulci, and finally, in some spec- phoenictis, from the early Oligocene, was 4 AMERICAN MUSEUM NOVITATES NO. 2694

and posterior limbs of the rhinal fissure that suggests incipient development of a sylvian sulcus. In addition, there was a presylvian sulcus delimiting a portion of the frontal lobe, the coronal sulci were bowed out laterally, and there is a small depression in the dorsal midline that suggests incipient devel- la opment of a cruciate sulcus. An incomplete endocast of Brachycyon, ec from middle Oligocene (Stampian) deposits near Marseilles, was described by Ginsburg (1966). It suggests a brain similar to that of Pseudocyonopsis, with a depression mark- ing the beginnings of a sylvian sulcus, and with a complete ectosylvian sulcus. There was a short sulcal notch between the caudal ends of the suprasylvian and ectolateral sulci (called the postlateral sulcus by Ginsburg), and a well-developed ectolateral sulcus 2 Cm. which did not contact the suprasylvian sul- FIG. 3. Daphoenodon superbus CM 1589A, cuscus.medialGinsburg'sto thefigurecoronalindicatessulcus,awhichsmall maysul- X3/4. Abbreviations: co, coronal stuc ec ilcus;l el, rc- indicate incipient development of a cruciate tolateral sulcus; es, ectosylvian sulc..us; la, lateral sulcus. dvlpet acuit sulcus; pr, presylvian sulcus; sg, Siigmoid gyrus; LATER A new wave of ss, suprasylvian sulcus; sy, sylvian AMPHICYONIDS: amphicyonids appeared in the early Miocene of North America (Arikareean, about 20 to 25 my), replacing the Oligocene daphoe- briefly described by Hunt (1974, p. 1037), nines, and endocasts are now available for who noted that it had an ectoliateral sulcus two genera, Daphoenodon and Temnocyon. developed as in Daphoenus, wi th its rostral The brain of Daphoenodon superbus (fig. 3) end confluent with the suprasyl[vian sulcus. is known from two endocasts, AM 27568 and The brain of Pseudocyonops,is is known CM 1589A. It appears to have been at a sim- from an endocast from the Fre-nch Quercy ilar stage as that of Pseudocyonopsis and Phosphorites, described by Beatamont (1964) Brachycyon, with incipient sylvian and well- under the name Amphicyon amibiguus. (The developed ectosylvian sulci, a relatively long species A. ambiguus was placesd in Pseudo- and arched suprasylvian sulcus (compared to cyonopsis by Ginsburg, 1966.) Pseudocyo- Daphoenus), a presylvian sulcus, and begin- nopsis ambiguus had a neocoortical sulcal nings of expansion of the sigmoid gyri (= pattern similar to that of Daphtoenus, with cortex between the coronal sulci). A trans- well-developed coronolateral, ectolateral, versely oriented depression within the sig- and suprasylvian sulci. The ecttolateral sul- moid gyrus may represent incipient devel- cus contacted the suprasylvian sulcus ros- opment of a cruciate sulcus. The ectolateral trally. It is not clear whether there was a sulcus did not contact the suprasylvian sul- notch between the caudal ends of the ecto- cus, there was a sulcal notch between the lateral and suprasylvian sulci. The brain of caudal ends of the ectolateral and suprasyl- Pseudocyonopsis was a bit more advanced vian sulci, and the entolateral sulcus was not than that of Daphoenus in havring a longer well developed. Details of cerebellar mor- entolateral sulcus, a more archied suprasyl- phology are blurred on the endocasts of Da- vian sulcus, a better developed[ ectosylvian phoenodon and the other post-Oligocene am- sulcus, and a notch at the junctio)n of anterior phicyonids, presumably owing to their 1980 RADINSKY: AMPHICYONID CARNIVORANS 5

L 2 cm. FIG. 4. Cynelos rugosidens, from the Gervais skull (MNHN), X3/4. Abbreviations: og, orbital gyrus; sg, sigmoid gyrus. relatively large size. The endocast from AM under the name Cephalogale rugosidens, 27568 is larger than that of CM 1589A, and then figured by Edinger (1929, fig. 127) as shows more neocortex between the supra- Amphicyon (Cephalogale) rugosidens, by sylvian sulcus and rhinal fissure. Piveteau (1961, p. 814 ) as Amphicyon am- The one endocast known for Temnocyon biguus, and by Beaumont (1962) as "Am- (F:AM 54134) suggests a brain similar to that phicyon" cf. rugosidens. A second Cynelos of Daphoenodon. The frontal region is shat- endocast, from a skull referred to as the Ju- tered in F:AM 54134, but one portion pre- lien skull by Hunt (1977), is also now avail- serves the imprint of a short sulcus that ex- able. tended rostrolaterally from the dorsal midline The brain of Cynelos (fig. 4) was slightly in the middle of the sigmoid gyrus, and prob- more advanced than that of Daphoenodon in ably represents the cruciate sulcus. having a more expanded sigmoid gyrus (cor- Endocasts of European amphicyonids that tex medial to coronal sulcus), with variably were approximate contemporaries of Da- developed dimples suggesting incipient sub- phoenodon and Temnocyon are known for divisions, and a more expanded orbital gyrus species of Cynelos and Ysengrinia, from the (rostral to the presylvian sulcus). The sylvian French St. Gerand-le-Puy Aquitanian depos- sulcus is represented by a short notch, and its (about 25 my). An excellent Cynelos en- the ectosylvian and suprasylvian sulci were docast was first described by Gervais (1872), about as tightly arched as in the more ad- 6 AMERICAN MUSEUM NOVITATES NO. 2694

2 cm. FIG. 5. Pliocyon cf. P. medius. F:AM 54334, X-34. Abbreviations: an, ansate sulcus; cr, cruciate sulcus; fp, fissura prima; pc, postcruciate dimple; pr, presylvian sulcus. vanced of the two Daphoenodon endocasts Thomas Farm middle Miocene (about 18 (AM 27568). The ectolateral sulcus contact- my). It shows relatively longer and more ed the suprasylvian sulcus in one but not the tightly arched ectosylvian and suprasylvian other of the two Cynelos endocasts, and the sulci, and a more sunken-in insular region entolateral sulcus was moderately well de- (within the arch of the ectosylvian sulcus), veloped in one but absent in the other. than in the older amphicyonid endocasts, The endocast of Ysengrinia preserves only suggesting a higher and more rostrocaudally a portion of the frontal lobe and olfactory compressed brain. The lateral gyrus was rel- bulb, and appears similar to corresponding atively narrow and there is no trace of an portions of the Cynelos endocasts. The sig- entolateral sulcus. The frontal region is not moid gyrus was equally expanded, and sub- preserved on this endocast, but a short sec- divided by secondary dimples. tion of the coronal sulcus is present, and its The next record of amphicyonid brains is curvature suggests that the sigmoid gyri were a partial endocast of Amphicyon, from the expanded at least as much as in Cynelos. 1980 RADINSKY: AMPHICYONID CARNIVORANS 7

Still more recent amphicyonid endocasts amphicyonid brains are expansion and in- are known from the Barstovian late Miocene creased folding of the neocortex, and in- (around 12 to 16 my), from Pliocyon cf. P. crease in relative brain size. Expansion and medius and Amphicyon frendens. The Plio- increased folding of the neocortex are nicely cyon endocast (F:AM 54334) is an excellent illustrated by a morphological series of en- specimen, with slight damage only in the docasts of Daphoenus-Cynelos-Pliocyon frontal region (see fig. 5). It indicates that the (fig. 6). Note the appearance and expansion brain of Pliocyon was advanced over that of of the orbital gyrus; the expansion of the sig- Cynelos and the older amphicyonids in hav- moid gyrus, reflected in the bowing out of ing a more expanded frontal lobe. Expansion the coronal sulcus and the eventual devel- of the sigmoid gyri is reflected in the bowed- opment of a cruciate sulcus; the lengthening out coronal sulci, the appearance of an an- and increasingly tight folding of the supra- sate sulcus, a laterally extending cruciate sylvian and ectolateral sulci, and the appear- sulcus, and a dimple representing the post- ance of ectosylvian and sylvian sulci as the cruciate sulcus. A long presylvian sulcus de- temporal lobe (and frontal lobe) expanded; limited an expanded orbital gyrus. The ec- and the increasing overlap of cerebellum by tosylvian and suprasylvian sulci were cerebrum. Similar trends in neocortical ex- relatively long and tightly arched, as in the pansion patterns can be seen in other fami- older Thomas Farm Amphicyon endocast lies of carnivorans (see, e.g., Radinsky, 1973, described above, and there was a short syl- 1975a), and the cruciate sulcus evolved in- vian sulcus. The lateral gyrus was relatively dependently at least five times (Radinsky, broad, and was subdivided by an entolateral 1971). sulcus. The occipital lobe overlapped the The expansion and increased folding of cerebellum more than in the older amphi- neocortex appears to indicate an increase in cyonids, extending to about the level of the relative amount of neocortex (compared to fissura prima of the vermis. rest of brain). However, that might not be The endocast of Amphicyon frendens the case. The apparent increase in relative (F:AM 54415) is dorsoventrally crushed and amount of neocortex may be accounted for, also shattered in the frontal region. From at least in part, by allometry-in particular, what is preserved, it appears that the sigmoid the scaling relationships of surface area to gyri were not expanded around a transverse- volume. Brains of later amphicyonids were ly oriented cruciate sulcus as in Pliocyon, larger than those of early amphicyonids, in but rather were dimpled, as in Cynelos. The part owing to the larger body size of the later lateral gyrus is relatively narrow, with no species, and in part to the trend towards in- trace of an entolateral sulcus, and the occip- creasing relative brain size (see table 1). As ital lobe did not cover as much of the cere- noted by Le Gros Clark (1947, and refer- bellum as in Pliocyon. ences cited therein), the neocortex is orga- The youngest amphicyonid endocast avail- nized as a thin sheet, and can increase only able is from an undescribed braincase (am- by areal expansion, while the underlying phicyonine, sp. indet., AM 2792), probably subcortical matter expands as a volume. from Clarendonian deposits (10-12 my). It is With increasing brain size there is relatively damaged in the occipital region and lacks the less surface area (since surface area is pro- cerebellum. In preserved portions it resem- portional to a radius squared while volume bles the Pliocyon endocast, and shows nice- is proportional to a radius cubed), and for ly the sigmoid gyri expanded around a ros- the neocortex sheet to keep pace, in volume, tralaterally oriented cruciate sulcus. with the increasing volume of subcortical tis- sue, it must expand disproportionately areal- ly. This is reflected in increased folding and DISCUSSION apparent relative expansion of the neocortex EVOLUTIONARY TRENDS: The main evo- over the rest of the brain with increasing lutionary trends seen in the fossil record of brain size. Whether there was an actual in- 8 AMERICAN MUSEUM NOVITATES NO0. 2694

TABLE 1 Relative Brain Size in Amphicyonids Skull Estimated Encephali- Length Body zation Endocast (SL, Body Length Weight Quotient Volume (cm3) cm) (cm) (gm)a (EQ)b Daphoenus hartshorni- 56 16.5 5.6 SLd = 92.4 18,594 0.64 anusc (AM 9757; SDSM 51121) Daphoenus vetusc 65r 18.5 5.6 SLd = 103.6 25,411 0.61 (PU 12588) Pseudocyonopsis ambiguus 68r 17.5r 5.6 SLe = 98 21,834 0.70 (GEN) Cynelos rugosidensc 115 24 5.0 SLf = 120 37,954 0.82 (LY) Daphoenodon superbus 133r 22.8 5.2 SLY = 118.6 36,723 0.97 (CM 1589) Pliocyon cf. P. medius 240 29.3r 4.5-5.0 SLh = 49,080- 1.19-1.44 (F:AM 54334) 131.9-146.5 65,438 aFrom the relationship between body length (L) and body weight (P) in 54 species of modern carnivores: P = 0.080 L273 (Radinsky, 1978, p. 820). bThe Encephalization Quotient (EQ) of a species is its brain size (E, gm or cma divided by the brain size expected in the average living mammal of that species' body weight (P, gm). In the average living animal, E = 0.12 P0f67. Thus EQi = Ei/0. 12 P1067. In a large suite of modern carnivores, EQ ranges from 0.53 to 1.60 (Radinsky, 1978, p. 823). CEQ estimates for these species differ slightly from those given in Radinsky, 1978, because additional data on skeletal dimensions allow improved estimates of body weights. dProportions from Scott and Jepsen, 1936, p. 74. eBody proportions modeled after Daphoenus. 'Proportions from Ginsburg, 1977, p. 42. gProportions from Romer, 1966, p. 237. hModeled after Cynelos (Ginsburg, 1977) and Amphicyon major (Bergounioux and Crouzel, 1973). r= restored.

crease in relative volume of neocortex com- tion of function (see, e.g., Welker and Cam- pared to the rest of the brain in amphicyonid pos, 1963). In amphicyonid brain evolution, brain evolution cannot be determined from such relative enlargement of a cortical area the available data. is evident primarily in the region of the cru- The parallel evolution of the same general ciate sulcus. The cortex around the cruciate pattern of neocortical convolutions with in- sulcus (sigmoid gyrus) contains fore and hind creasing brain size in various carnivoran limb representation in primary somatic sen- lines-in particular, the pattern of arcuate sory (tactile) and motor areas, and the mul- folds arranged concentrically around the syl- tiple independent development of the cru- vian sulcus-may reflect constraints on fold- ciate sulcus in carnivoran brain evolution ing patterns imposed by inheritance of a may reflect expansion of motor cortex for common pattern of thalamocortical connec- improved locomotor control (see discussion tions from the Eocene common ancestor of in Radinsky, 1971). Early stages of expan- modern carnivorans. sion of the sigmoid gyrus in amphicyonids Disproportionate expansion of a particular were marked by dimpling of the gyrus (see area of the neocortex may reflect specializa- figs. 3 and 4), while in canids and felids the 1980 RADINSKY: AMPHICYONID CARNIVORANS 9

Cyn e /os

--1 ~~~~2Cm. Pllo cyvon FIG. 6. Endocasts of Daphoenus, Cynelos, and Pliocyon to illustrate the evolutionary trend of expansion of neocortex through time. Abbreviations: co, coronal sulcus; cr, cruciate sulcus; es, ectosylvian sulcus; la, lateral sulcus; og, orbital gyrus; ss, suprasylvian sulcus; sy, sylvian sulcus. All to scale, approximately xO.8. only infolding was the cruciate sulcus itself brains) when sigmoid gyrus expansion be- (see figures in Radinsky, 1973, 1975a). The gan. reason for that difference is not apparent. It The trend toward increase in relative brain may reflect the larger size of the amphicyo- size is apparent in even the small sample of nid brain (compared to canid and felid amphicyonid endocasts now available to us 10 AMERICAN MUSEUM NOVITATES NO. 2694

(table 1). The earliest amphicyonids had En- cus was short, and it was only around 15 my, cephalization Quotients (EQs) of around 0.60 that it appeared as extensive in canids as in to 0.70, apparently advanced over that of amphicyonids (see figures in Radinsky, their Eocene miacid ancestors (0.44-0.52 for 1973). Since the ectolateral sulcus is present late Eocene Procynodictis; Radinsky, 1978). in only a few mustelids, it obviously evolved Five to 10 million years later, Cynelos and independently in those forms. However, the Daphoenodon had EQs of 0.82 and 0.97, re- presence of an ectolateral sulcus in the ear- spectively, which is within the EQ range of liest canids and amphicyonids is a shared living carnivorans (Radinsky, 1978). Finally, derived character that may reflect inheri- one of the latest amphicyonids, Pliocyon, tance from a common ancestor. apparently had an EQ between 1.19 and 1.44, In modern canids the ectolateral sulcus which is high even for modern carnivorans. appears to form the rostral border of a sec- Increase in relative brain size is a common ondary visual field (Radinsky, 1973, fig. 11). evolutionary trend in mammals, and its sig- The appearance of the ectolateral sulcus in nificance remains a fascinating, open ques- early canids and amphicyonids may there- tion. fore reflect early expansion of visual cortex PHYLOGENETIC SIGNIFICANCE: It has long in those families. Such expansion could have been recognized that differences in cortical occurred independently, or may have been folding patterns distinguish various families inherited from a common ancestor shared of modern carnivorans (Mivart, 1855, and after divergence from the other carnivorans. references cited therein). Canids, felids, vi- Two recent experts on amphicyonids have verrids, and the arctoid group have distinc- concluded that amphicyonids are closer phy- tive patterns (Radinsky, 1973, 1975a and logenetically to ursids than to any other car- 1975b). The brains of amphicyonids also had nivorans. Hunt (1977) stressed their common a distinctive pattern of cerebral convolu- possession of an enlarged inferior petrosal tions, characterized by the presence of a long venous sinus that contains (or contained) a ectolateral sulcus that usually extended to loop of the internal carotid, a specialization contact the suprasylvian sulcus, a short sul- for cooling blood to the brain, and a unique cus between the caudal ends of the ectola- shared derived character in ursids and am- teral and suprasylvian sulci, and, in all but phicyonids. Ginsburg (1977) noted that fea- the earliest species, an ectosylvian sulcus ture plus other aspects of cranial circulation that was an unbroken arch and remained ex- and limb morphology shared by ursids and posed (unopercularized) on the lateral sur- amphicyonids. To me the most impressive face of the brain. similarity between amphicyonids and ursids An ectosylvian sulcus expressed as a com- is the cranial circulation modification (ca- plete arch evolved independently in many rotid loop in inferior petrosal sinus). If that groups of carnivorans in addition to amphi- shared derived character was inherited from cyonids (paleofelids, canids, ursids, ota- a common ancestor of amphicyonids and ur- riids), and in the ursids and otariids it be- sids, then the ectolateral sulcus evolved in- came opercularized, buried by expansion of dependently in canids and amphicyonids (as surrounding gyri (=a derived condition). The it has done in a few recent mustelids). On short sulcus between ectolateral and supra- the other hand, if the shared derived char- sylvian sulci occurred only in amphicyonids acter of the ectolateral sulcus in canids and and, as a variable feature, in a few genera of amphicyonids was inherited from a common early canids (e.g., Mesocyon). The ectolat- ancestor, then the cranial circulatory modi- eral sulcus is rare among carnivorans. Be- fications evolved independently in ursids and sides amphicyonids, it occurs only in canids amphicyonids. In the absence of information and a few species of modern mustelids (Eira on how easy it is (morphogenetically) to barbara, Galictis vittatus, and Martes fla- modify either the cortical pattern or the cra- vigula: Theide, 1966, and personal observa- nial circulation, I see no compelling argu- tions). In the early canids the ectolateral sul- ment for choosing one or the other of those 1980 RADINSKY: AMPHICYONID CARNIVORANS I1I alternatives. Of course, another possibility (Mammalia, Amphicyonidae) from the is that both derived features evolved inde- Oligocene of North America. Jour. Pa- pendently in amphicyonids. leont., vol. 48, pp. 1030-1047. 1977. Basicranial anatomy of Cynelos Jour- LITERATURE CITED dan (Mammalia: Carnivora), an Aqui- tanian amphicyonid from the Allier Ba- Beaumont, G. de sin, France. Ibid., vol. 51, pp. 826-843. 1962. Observations sur lFost6ologie cranienne Piveteau, J. (ED.) et la position systematique des petits 1961. Trait6 de Paleontologie, vol. 6 (1), "Amphicyon" de l'oligocene europeen. Mammiferes. Encephales de carnivores Bull. Soc. Vaud. Sci. Nat., vol. 68, no. fossiles. Paris, Masson et Cie., pp. 806- 307, pp. 81-92. 820. 1964. Un crane d'Amphicyon ambiguus (Fil- Mivart, St. G. hol) (Carnivora) des Phosphorites du 1855. Notes on the cerebral convolutions of Quercy. Arch. Sci. Geneve, vol. 17, pp. the Carnivora. Jour. Linn. Soc., vol. 19, 331-339. pp. 1-25. Bergounioux , F., and F. Crouzel Radinsky, L. 1973. Amphicyon major Blainville du Mio- 1971. An example of parallelism in carnivore cene moyen de Sansan (Gers). Ann. Pa- brain evolution. Evolution, vol. 25, pp. leont. (vert.), vol. 59, pp. 27-52. 518-522. Bonis, L. de 1973. Evolution of the canid brain. Brain, Be- 1969. Remarques sur la position systematique hav., Evol., vol. 7, pp. 169-202. des Amphicyon. C.R. Acad. Sci. Paris, 1975a. Evolution of the felid brain. Ibid., vol. vol. 269, ser. D, pp. 1748-1750. 11, pp. 214-254. Le Gros Clark, W. E. 1975b. Viverrid neuroanatomy: phylogenetic 1947. Deformation patterns in the cerebral and behavioral implications. Jour. cortex. pp. 1-22 In Clark, W. E. Le Mammalogy, vol. 56, pp. 130-150. Gros and P. B. Medawar (eds.), Essays 1978. Evolution of brain size in carnivores on growth and form presented to and ungulates. Amer. Nat., vol. 112, pp. D'Arcy Wentworth Thompson. Oxford, 815-831. Clarendon Press. Romer, A. S. Edinger, T. 1966. Vertebrate Paleontology, Chicago, Univ. 1929. Die fossilen Gehirne. Ergebn. Anat. Ent- Chicago Press. 468 pp. wickl., vol. 28, pp. 1-249. Scott, W. B., and G. L. Jepsen 1956. Objets et resultats de la paleoneurolo- 1936. The mammalian fauna of the White Riv- gie. Ann. Paleont. (vert.), vol. 42, pp. er Oligocene. Pt.1 Insectivora and Car- 97-116. nivora. Trans. Amer. Philos. Soc., vol. Gervais, P. 28, pp. 1-153. 1872. Forme cerebrale du Cephalogale geof- Thiede, U. froyi. Jour. Zool., vol. 1, pp. 131-133. 1966. Zur Evolution von Hirneigenschaften Ginsburg, L. mitteleuropiiischer und siidamerika- 1966. Les amphicyons des Phosphorites du nischer Musteliden. Z. zool. Syst. Quercy. Ann. Paleont. (vert.), vol. 52, Evol., vol. 4, pp. 318-377. pp. 23-64. Welker, W. I., and G. B. Campos 1977. Cynelos lemanensis (Pomel), carnivore 1963. Physiological significance of sulci in so- urside de l'Aquitanien d'Europe. Ibid., matic sensory cerebral cortex in mam- vol. 63, pp. 57-104. mals of the family Procyonidae. Jour. Hunt, R. M., Jr. Comp. Neurol., vol. 120, pp. 19-36. 1974. Daphoenictis, a cat-like carnivore