A NEW FOSSIL TURTLE, KINOSTERNON ARIZONENSE,FROM ARIZONA.
By Charles W. Gilmore,Associate Curator, Division of Paleontology , United States National Museum.
INTRODUCTION.In a collection of vertebrate fossils made by Dr. J. W. Gidley inthe spring of 1921, near Benson, Cochise County, Arizona, were twowell-preserved turtle specimens, the first extinct representative of thefamily Kinosternidae to be found in North America. It is also ofinterest that they are the male and female of a new species aboutto be described. Both specimens were found in the same depositof fossils, within a few feet of one another, and associated with aconsiderable fauna consisting of mammal and bird remains.Eight species of the genus Kinostemon are recognized in NorthAmerica by Stejneger^ and Barbour, of which only two, Kinostemonsononense LeConte and K.Jiavescens (Agassiz) are said to range intoArizona. It is the latter species to which the fossil form appears tobe most nearly related.I wish at this time to express my appreciation of the assistancegiven me by Dr. Leonhard Stejneger of the United States NationalMuseum, especially in the comparison of the fossil with the extantspecies of Kinosternidae, a work that was made comparatively easybecause of his intimate knowledge of the living species.Family KINOSTERNIDAE.^'Nuchal plate produced into costiform processes, underlying themarginals. Plastral bones eight, the entoplastron being absent.Shell covered with epidermal shields. Caudal vertebrae procoelus.Neck completely retractile within the shell. Temporal region notroofed over ; no parieto-squamosal arch. Digits moderately elongate
;
phalanges with condyles; claws four or five. ^^
I A check List of North American Amphibians and Reptiles, Harvard University Press, 1917, pp.
"'">The definition of the family and genus is that given by Dr. G. A. Boulenger in his Catalogue of theChelonians, Rhynocephalians, and Crocodiles in the British Museum (new ed.), 1889, p. 33.No. 2451-Proceedings U. S. National Museum. Vol. 62. art. 5.
PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 62Genus KINOSTERNON Spix.Carapace more or less depressed; marginal sliields, one azygosnuchal and 11 pairs. Plastron articulating with the marginals by-suture, front and hind lobe moveable; gular shield single or absent;pectoral shields not extending on the bridge. Postorbital and tem-poral arches moderate. Digits webbed; fingers all clawed, outertwo clawless. Tail short.KINOSTERNON ARIZONENSE, new species.Plates 1 to 5.Type.?Male. Cat. No. 10463, U.S.N.M.; consists of the nearlycomplete carapace and plastron, the latter lacking the anterior lobe;lower jaws, fragmentary verte-brae, limb bones, etc.Paratype.?Female. Cat. No.10462, U.S.N.M.; consists of thenearly complete carapace andplastron.Type-locality.?^Benson Local-ity Quarry, two miles south ofBenson, Cochise County, Ari-zona.Horizon .?Pliocene
.
Collector.?J. W. Gidley, 1921.When found the specimenswere entirely disarticulated andbroken into numerous pieces,and the assembling of these por-tions has resulted in some dis-tortion and other imperfectionsin the carapace as may be ob-served in the illustrations (seepis. 1 and 3). Some small areasof both upper and lower shellswere missing, although as a wholethey are in a remarkably goodstate of preservation.The much larger size of the fossil forms at once distinguishes themfrom any living species, and I therefore propose the name KinosUr-non arizonense for their reception.A comp rison of the two specimens show them to be very similar,in the extent and arrangement of the various bony elements, aswell as the epidermal shields which covered the osseous parts in Hfe.That the larger specimen is a male appears to be shown by the con-cavity of the posterior lobe, the swelhng outward of the lateral bordersof this lobe back of the inguinal notch, and the fact that it fills this
Fig. 1. Cakapace of Kinosteenon aeizonense.No. 10463, U.S.N.M. Type. Male. C. 1, C. 8,COSTAL BONES 1 AND 8; N, 1, 2, 3, 4, 5, 6, NEURALBONES 1 TO 6; Nu, NUCHAL BONE; PEB 10, TENTHPEEIPHERAL BONE; PY, PYGAL BONE; SPY, SUPRA-PYGAL bone: VI, V5, VERTEBRAL SCUTES 1 AND 5.One-half natural size.
ART. 5. A NEW FOSSIL TURTLE GILMORE.part of the carapace less completely than in the female, specimenNo. 10462, U.S.N.M. (See pis. 2 and 4.) With the exception of theconsiderable difference in size of the two these are exactly the differ-ences to be observed between the sexes of K. Jlavescens, as is shownby specimens Cat. Nos. 22671 and 19058, U.S.N.M.While there are other characters, to be pointed out later, whichindicate the affinities of K. arizonense to be nearest to E. Jlavescens,the sudden enlargement of the marginal scutes beginning with theninth, see figs. 3 and 4, which arises well above the middle of the eighthperipheral, whereas the superior terminations of those anterior barelyreach the middle and are usuallybelow, are precisely the conditionsfound in K. Jlavescens, a characterwhich Doctor Stejneger assures meis constant for that species, andone which serves to distinctly sep-arate it from all other members ofthe genus.In outline the carapace of K.arizonense is broadly oval, slightlyexcavated above the neck (see fig.2), the hinder end evenly roundedwith a slight median V-shapednotch. The length of the carapaceof the paratype in a straight line is148 millimeters. It is estimatedthat the carapace of the type whichlacks some of the median anteriormargin, would slightly exceed 170millimeters in length. In widththe type measures 118 millimeters;the paratype 108 millimeters;height at the center, type 73 milli-meters, paratype 47.5 millimeters.The surfaces of the shell are smooth, there being no indications ofridges or carinae, such as are found in some of the living species ofthe genus. The sulci are narrow and well impressed. The bone ofboth carapace and plastron is relatively thin. The free margins ofthe peripherals present a sharp edge, those posterior to the inguinalnotch having a tendency to flare upward.The paratype (pi. 3) shows the presence of a good sized nuchalslightly excavated for the neck on the free border, which measures21 miUimeters wide; the greatest width of this bone is 36 millimeters.It cannot be determined from the present specimens whether thenuchal was in contact with the first neural or whether these elements
Fig. 2. Carapace of Kinosternon arizonense.No. 10462, U.S.N.M. Paratype. Female.C. 1, C. 8, costal bones 1 AND 8; N, 1, 2, 3, 4,5, 6, NEURAL bones 1 TO 6; Nu, NUCHALBONE;per 10, TENTH PERIPHERAL BONE; PY, PYGALbone; spy, suprapygal bone; VI, V5, verte-bral SCUTES 1 to 5. One-half natural size.
PROCEEDINGS OF THE NATIONAL MUSEUM. VOL 62.
were separated by the intervention of the first costals meeting on themedian line as in Kinosternon leucostomum as figured by Boiilenger.'In the type there are six neurals, all except the sixth being present.That a reduced sixth neural existed is clearly indicated by the exca-vated ends of the sixth pair of costals which unite on the median lineposterior to the sixth neural, as shown in Figure 1 . All except thesixth are longer than wide.Measurements of neurals in millimeters.
No.
AST. 5. A NEW FOSSIL TURTLE GILMORE.Measurements of vertebrals in millimeters.
6 PROCEEDINGS OF THE NATIONAL MUSEUM.The posterior lobe is 51 millimeters long and 57 millimeters wideat the base, whereas in the much larger type (male) specimen, thelength of this lobe at the center is only 46.5 millimeters, and 53millimeters wide at the base, but which expands posteriorly to 68millimeters wide. It will thus be observed that the posterior lobein the male is relatively much smaller than in the smaller female,compare Figures 5 and 6, a difference that prevails in the two sexesof the living K. flavescens. The posterior end is indented by aU-shaped notch, 7.5 millimeters deep and 10 millimeters wide in the
Fig. 5. Plasteal view of carapace of Kinoster Fig. 6. Plastron of Kinosternon arizonensk.kon aeizonense. no. 1m63, u.s.n.m. type.Male, ab, abdominal scute; an, anal scute;PEM, femoral scute; hyo, hyoplastral bone;HYPO, HYPOPLASTRAL BONE; XIPH, XIPHIPLASTRALBONE. One-half natural size.
No. 10462, U.S.N.M. PAR.4.TYPE. FEMALE. AB,ABDOMINAL SCUTE; AN, ANAL SCUTE; EPI, EPIPLAS-TRAL bone; hyo, HYOPLASTRAL BONE; HYPO, HYPO-PLASTRAL BONE; XIPH, XIPHIPLASTRAL BONES. MOBETHAN ONE-HALF NATURAL SIZE.
male but only slightly indented in the female. The posterior ex-tremities of the plastron end about 27 millimeters anterior to theposterior margin of the carapace. In the puratype this distance isonly 18 millimeters. The bridge in the type has a width of 25 milli-meters, but in the smaller paratype it measures 29 millimeters foreand aft. The plastron at the center of the bridge in the typemeasures 99 millimeters in width; the paratype 92 millimeters.The free borders of the plastra are acute on both front and hinderlobes, thickening slightly from the border inward, but nowheredoes the plastron exceed 4 millimeters in thickness. The bevelled
ART. 5. A NEW FOSSIL TURTLE GILMORE.
superior lateral borders on both front and back lobes are compara-tively narrow as is well shown in Figure 7 and Plate 5.Measurements of plastral hones and dermal scutes in millimeters.
Length of epiplastral boneLength of hj'oplastral l)one on median line...Length of hypoplastral lione on median line.Length of xiphiplastral bone on median line. 1722.535
ParatypeNo. 10462,female.
DERMAL SCUTES.Length of gular scute on median lineLength of humeral scute on median line...Length of pectoral scute on median line...Length of abdominal dcute on median line.Length of femoral scute on median lineLength of anal scute on median line
40151941
201823217.526The single triangular gular scute extends posteriorly one-half thelength of the anterior lobe, (see pi. 4), but in four specimens of A'.flavescens, now before me, this scuteonly extends posteriorly one-thirdthe length of the anterior lobe, be-cause of this the humerals in the liv-ing species are correspondingly longon the median line. The paratypeagrees with the extant species inhaving the pectorals meeting nar-row on the median line. Boulen-ger,'' however, in his definition of thespecies flavescens distinguishes it byhaving ''pectoral suture nearly aslong as that between humerals (inthe adult)." Yet no specimens avail-able to me in the National Museumcollections show such a condition,all being short. K. flavescens alsodiffers from the fossil species in hav-ing narrow femorals and pointed tri-angular anals. In K. arizonensethese scutes at the center are of nearly equal length. On the bridgeare two transversel}^ narrow inframarginal scutes, the anterior onebeing very much smaller than the posterior. These scutes liealmost wholly on the plastral bones. (See figs. 5 and 6).
Fig. 7. Pla.stkon or Kinosternon arizo"NENSE. No. 10462, U.S.N.M. Paratype.Female. Superior view, epi, epiplas-TR.iL bone; hyo, hyoplastral bone; hypo,HYPOPLASTRAL BONE; 5TH PER, fiTH PER,PERIPHERAL BONES 5 AND G; XIPH, XIPIHI-PLASTRAL. One-half natural .size.
< Catalogue of the Cheloniaa.s, Rhynocephalians, and Crocodiles in the British Museum, 1SS9, p. 40.G0466?23?Proc.X.M.voI.62 23
8 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 62.Kinosternon arizonense apparently has its closest affinities withK. Jiavescens which now ranges into this same part of Arizona. Itmay be distinguished at once from that species by its much largersize; the more rounded anterior extension of the anal scutes, ascontrasted with their longer and more pointed triangular shape in K.Havescens, which bring about a reduction of the femorals on themedian line. Other differences might be pointed out such as thereduced number of neurals, broader anterior lobe, etc., but DoctorStejneger, who has made an exhaustive study of the Kinosternidae,tells me that many of these features are so inconstant they cannotbe relied upon for specific differentiation.EXPLANATION OF PLATES.Plate 1.Carapace of Kinosternon arizonense. Cat. No. 10463, U. S. N. M. Type. Male.Superior view. About | natural size.Plate 2.FlsLStron oi Kinosternon arizonense. No. 10463, U.S. N.M. Type Male. Ven-tral view. About f natural size. Plate 3.Carapace of Kinosternon arizonense. No. 10462, U.S.N.M. Paratype. Female.Superior view. About natural size.Plate 4.Plastron of Kinosternon arizonense. No. 10462, U.S.N.M. Paratype. Female.Ventral view. Natural size. Plate 5.Plastron of Kinosternon arizonense. No. 10462, U.S.N.M. Paratype. Superiorview. Natural size.
U. S. NATIONAL MUSEUM PROCEEDINGS, VOL. 62, ART. 5 PL . I
Carapace of Kinosternon arizonense.For explanation of plate see page
U. S. NATIONAL MUSEUM PROCEEDINGS, VOL.. 62, ART. 5 PL. 2
Plastron of Kinosternon arizonense.For explanatjon of plate see page
U. S. NATIONAL MUSEUM PROCEEDINGS, VOL. 62, ART. 5 PL. 3
Carapace of Kinosternon arizonense.For explanation of plate see page 8.
U. S. NATIONAL MUSEUM PROCEEDINGS, VOL. 62, ART. 5 PL. 4
PLASTRON OF KiNOSTERNON ARIZONENSE.FOR EXPLANATION OF PLATE SEE PAGE 8
U. S. NATIONAL MUSEUM PROCEEDINGS, VOL. 62, ART. 5 PL. 5
Plastron of Kinosternon arizonense.For explanation of plate see page