A New Tortoise, Genus Gopherus, From North-Central Mexico

Part 1

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UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY

Volume 11, No. 5, pp. 335-343, pls. 7 and 8 April 24, 1959

A New Tortoise, Genus Gopherus, From North-central Mexico

JOHN M. LEGLER

UNIVERSITY OF KANSAS LAWRENCE 1959

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Robert W. Wilson

Volume 11, No. 5, pp. 335-343 Published April 24, 1959

UNIVERSITY OF KANSAS Lawrence, Kansas

PRINTED IN THE STATE PRINTING PLANT TOPEKA, KANSAS 1959

A New Tortoise, Genus Gopherus, From North-central Mexico

JOHN M. LEGLER

In the course of taxonomic studies of the genus Gopherus it was found that specimens from north-central Mexico belong to an hitherto unrecognized species, which is named and described below.

Gopherus flavomarginatus new species

Holotype.--U.S. National Museum 61253, adult; stuffed specimen with disassociated skull; 30 to 40 miles from Lerdo, Durango, Mexico; obtained by Dr. Elswood Chaffee, 1918.

Paratypes.--USNM 61254, adult, stuffed specimen with skull in place, other data the same as those for holotype; USNM 60976, adult, stuffed specimen with disassociated skull, Lerdo, Durango, Dr. Elswood Chaffee, May 1918; University of Illinois 42953-4, adults, two carapaces, Carrillo, Chihuahua, Pete S. Chrapliwy and Kenneth L. Williams, 1 August 1958; University of Kansas 39415, adult, carapace only, 8 mi. E and 2 mi. S Americanos, Coahuila, Robert W. Dickerman, 19 May 1954.

Diagnosis.--A large tortoise of the genus Gopherus, having a flat-topped, posteriorly-flared shell, carapacal laminae that are pale with contrasting dark centers (at least on the lateral margins of the carapace), intergular seam longer than interhumeral, obtuse gular projections, and a relatively wider skull than other Mexican representatives of the genus.

Description of species.--Ground color of carapace pale yellow to straw in smaller specimens, pale brown in larger specimens; in some specimens a slight indication of darker radial markings on carapace; epidermal areolae of carapace (if present) and first two or three zones of growth (around areolae) dark brown to black, their contrast with the ground color greater in smaller specimens; ground color of lateral marginals yellowish, much paler than remainder of carapace; black areolae of marginals contrasting sharply with ground color even in old individuals; plastron pale, approximately the same shade of yellow as lateral marginals, marked with sharply contrasting blotches of black or dark brown in younger specimens, becoming immaculate with age.

Carapace low, evenly arched or slightly flat-topped in cross section, its height slightly more than 50 per cent of its length; top of carapace, between highest parts of first and fourth central laminae, more or less flat in profile; carapace flared, wider posteriorly than anteriorly; central laminae all broader than long, the first not (or but slightly) narrower posteriorly than anteriorly; plastron deeply notched behind, the inner margins of the notch straight, neither convex nor concave; gular projections truncate (not pronglike) having no notch or but a shallow notch between them; greatest combined width of gular laminae much greater than greatest length; interlaminal length of gular greater than that of humeral; one large axillary scute on each side, approximately rectangular but slightly wider below than above; one or two inguinal scutes on each side, the anterior roughly triangular and much larger than posterior.

Anterior surface of antebrachium having enlarged, juxtaposed (or slightly imbricated), osteodermal scales arranged in seven to eight longitudinal rows, each scale yellowish with a black or dark brown center; scales on lateral edge of antebrachium, from fifth claw to elbow, ten in number and darker than other antebrachial scales; two enlarged black-tipped, yellow spurs on posterior surface of thigh, inner spur approximately half the size of outer. Head relatively wide, greatest width of skull slightly more than 80 per cent of condylobasilar length; width of head 1.3 to 1.7 times diameter of hind foot; scales on top of head large but irregularly arranged (see table 1 for measurements of type and paratypes).

TABLE 1. Measurements, in Millimeters, of the Holotype and Paratypes of Gopherus Flavomarginatus New Species

----------------+--------+--------+--------+------+---------+------ Catalogue Number|Length |Width |Length | |Diameter |Width and Collection |of |of |of |Height|of |of |carapace|carapace|plastron| |hind foot|head ----------------+--------+--------+--------+------+---------+------ USNM 60976 | 246 | 212 | 252 | 108 | 31 | 41 ----------------+--------+--------+--------+------+---------+------ USNM 61253 | 222 | 166 | 212 | 96 | 21 | 36 ----------------+--------+--------+--------+------+---------+------ USNM 61254 | 371 | 292 | 358 | 157 | 43 | 55 ----------------+--------+--------+--------+------+---------+------ IU 42953 | 281 | 220 | | | | ----------------+--------+--------+--------+------+---------+------ IU 42954 | 278 | 214 | | | | ----------------+--------+--------+--------+------+---------+------ KU 39415 | 303 | 232 | | | | ----------------+--------+--------+--------+------+---------+------

Duges (1888:146-147, and 1896:479) twice reported specimens of Gopherus polyphemus from Chihuahua (see discussion of distribution); his description of two living examples (1888) agrees generally with the above description of G. flavomarginatus. He stated that the iris of his smaller specimen was yellow and the iris of a larger specimen brown.

It will be most interesting to learn the color of juveniles of G. flavomarginatus. Considering the dark color of the epidermal areolae of adults, I would expect the color of hatchlings to be dark brown to nearly black, with each lamina acquiring paler borders as it grew, rather than acquiring darker borders as is usually the case in G. berlandieri (personal observation), agassizii (Miller, 1932:194, pl. 2; Woodbury and Hardy, 1948:165, figs. 9 and 10), and polyphemus (personal observation).

PLATE 7. Gopherus flavomarginatus new species: Top--Dorsal and ventral views of holotype (× 1/3); Middle--Lateral view of holotype (× 1/3); Bottom--Head of paratype (USNM 61254) (× 1/2) and antebrachium of holotype (× 5/6). Dark outline on plastron of holotype indicates where portion of shell was removed (and then replaced) in course of preparation.]

PLATE 8. Gopherus flavomarginatus new species: Dorsal views of paratypes (from top to bottom, IU 42953, IU 42954, and KU 39415), approximately 1/5 natural size.]

Anomalies.--There is a high incidence of anomaly in the type series. Three of the specimens (USNM 60976, IU 42954, and KU 39415) have a supernumerary central lamina. All of the specimens from Durango are anomalous in regard to the marginal laminae. In the holotype the first marginals are small, approximately as wide as the small precentral. In the largest paratype (USNM 61254) the first and second marginals are fused to form a single large scute on each side. In the remaining Durangan paratype (USNM 60976) there are eleven normal marginals on each side but a supernumerary lamina occurs between the first and second marginal on the left and between the precentral and first marginal on the right side. The remaining three paratypes have the number of marginals that is normal for the genus.

Part 2

Relationships.--Gopherus flavomarginatus differs from all other species of the genus by its larger size and by having an intergular seam that is longer than the interhumeral seam. The possession of a single, rectangular axillary scale, wider below than above, also tends to distinguish flavomarginatus from other living Gopherus; in the other species this scute (frequently paired in berlandieri) is generally triangular or at least pointed below. Femoral spurs are developed to varying degrees in the other species of Gopherus; they are usually lacking in individuals of small to medium size. In large specimens of agassizii and polyphemus that I have examined, there is but one enlarged spur, although several pointed osteodermal scales may be present on the back of the thigh.

Gopherus berlandieri, the closest relative of G. flavomarginatus in a geographic sense, has a highly arched shell and pronglike gular projections, between which there is nearly always a deep notch. Gopherus agassizii, morphologically the closest Mexican relative of flavomarginatus, differs from it in having a narrower head and in lacking the contrasting pale and dark coloration of the plastron and lateral marginal area. Gopherus polyphemus seems to be the closest relative of flavomarginatus and differs from it in having an unflared shell (anterior and posterior widths of carapace subequal or carapace narrower behind) and in the characteristics of color mentioned above. Certain proportional differences between the living species of Gopherus are summarized in table 2.

Distribution.--The discovery of a new Gopherus from north-central Mexico increases to four the recognized forms of the genus and extends the known range of the genus onto the Mexican highlands, approximately 410 miles eastward from Alamos, Sonora (G. agassizii), approximately 100 miles westward from a point 2 mi. W of Monclova, Coahuila (G. berlandieri), and approximately 200 miles westward from Monterrey, Nuevo León (G. berlandieri).

TABLE 2. Bodily Proportions in the Known Species of Gopherus. Two Specimens of G. polyphemus from Harmon, Mississippi (USNM 53166-7), Are Considered Separately Because of Their Notably Narrower Heads. The Size of Each Sample Is Given in Parentheses Above the Average; Extremes Are in Parentheses Following the Averages.

---------------------+-----------+-------------+-------------+-------- Species |Greatest |Height | Height |Diameter and |width of |of | of |of General Locality |skull as a |shell as a | shell as a |hind foot |percentage |percentage | percentage |as a |of |of width | of length |percentage |condy- |of | of |of width |lobasilar |carapace | carapace |of head |length | | | ---------------------+-----------+-----------+------------+---------- G. polyphemus | (6) |(13) |(13) | (Florida) |.94 |.53 |.39 | |(.92-.97) |(.48-.58) |(.36-.42) | ---------------------+-----------+-----------+------------+---------- G. polyphemus |(2) |(2) |(2) | (Mississippi) |.87 |.53 |.43 | |(.84-.89) |(.52-.54) |(.40-.45) | ---------------------+-----------+-----------+------------+---------- G. berlandieri |(21) |(22) |(21) | (Texas and NE Mexico)|.78 |.56 |.46 | |(.70-.83) |(.48-.62) |(.43-.51) | ---------------------+-----------+-----------+------------+---------- G. agassizii |(6) |(8) |(8) | (U.S. and N. Sonora) |.77 |.53 |.41 |(.38-.44) | |(.70-.83) |(.49-.58) | | ---------------------+-----------+-----------+------------+---------- G. agassizii | |(4) |(4) |(4) (Alamos, Sonora) | |.56 |.39 |.92 | |(.52-.59) |(.37-.41) |(.87-1.00) ---------------------+-----------+-----------+------------+---------- G. flavomarginatus |(2) |(3) |(3) |(3) (North-central | | | | Mexico) |.83 |.54 |.43 |.71 |(.82-.83) |(.51-.58) |(.42-.44) |(.58-.78) ---------------------+-----------+-----------+------------+----------

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