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Title: A New Extinct Emydid Turtle from the Lower Pliocene of Oklahoma
Author: Galbreath, Edwin C.
Language: English
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*** Start of this LibraryBlog Digital Book "A New Extinct Emydid Turtle from the Lower Pliocene of Oklahoma" ***
A New Extinct Emydid Turtle from the Lower
Pliocene of Oklahoma
BY
EDWIN C. GALBREATH
University of Kansas Publications
Museum of Natural History
Volume 1, No. 16, pp. 265-280, plate 1
August 16, 1948
University of Kansas
LAWRENCE
1948
UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY
Editors: E. Raymond Hall, Chairman; H. H. Lane, Edward H. Taylor
Volume 1, No. 16, pp. 265-280, plate 1
August 16, 1948
UNIVERSITY OF KANSAS
Lawrence, Kansas
PRINTED BY
FERD VOILAND, JR., STATE PRINTER
TOPEKA, KANSAS
1948
22-3340
[Illustration: PLATE 1. _Chrysemys limnodytes._ Univ. Kans.
Mus. Nat. Hist., Vert. Paleo. Coll. No. 7676. Fig. A, dorsal
view of carapace; fig. B, ventral view of plastron. Both views
approximately × .4.]
A New Extinct Emydid Turtle from the Lower Pliocene
of Oklahoma
By
EDWIN C. GALBREATH
In the summer of 1946 a party from the University of Kansas Museum of
Natural History visited exposures of the Laverne formation in Beaver
County, Oklahoma, at the invitation of Dr. Stuart Schoff of the United
States Geological Survey. When examining the marl beds an Emydid turtle
was discovered which appears to be an unnamed species of the genus
_Chrysemys_. A description of the new species follows.
Chrysemys limnodytes, new species
_Holotype._--University of Kansas Museum of Natural History No.
7676, vertebrate paleontological collection, a turtle consisting of
a fragmental anterior portion of a carapace, left part of the
plastron, and several marginals collected by the 1946
paleontological field party of the University of Kansas Museum of
Natural History.
_Geological Age and locality._--Marl beds of the Laverne formation,
early Pliocene age, in SW 1/4 Sec. 15, T. 4 N., R. 25 ECM, Beaver
County, Oklahoma. The specimen was removed from the marl
immediately below the fossil leaf zone (see Chaney and Elias, 1936;
Frye and Hibbard, 1940).
_Diagnosis._--Size large (see measurements) and differing from
other species of _Chrysemys_ in having: The anterior end of the
carapace broadly concave, the posterolateral marginals not greatly
flared, the posterior end of the plastron broadly indented, the
carapace more sculptured and relatively wider.
_Description of type._--The specimen had been badly damaged before
preservation, and had suffered further damage from exposure before
discovery. The anterior and posterior lobes of the plastron had been
folded over the bridge, forming a three-ply thickness of bone. Of the
carapace, only the following parts are known: Fragment of the nuchal;
right 1st, 7th, 8th, and 9th marginals, left 1st, 2d, 7th, 8th, 9th, and
11th marginals; costals 1-5 on the right side; costals 1-4 on the left
side; and 1st, 2d, 3d, and 4th neurals. The left half of the plastron is
relatively complete, lacking only the epiplastron and entoplastron. The
left 7th, 8th, and 9th marginals are joined to the plastron at the
inguinal buttress, and the right 7th, 8th, and 9th marginals are
attached to the fifth costal. The carapace has smooth contours with no
keel present, but on the lower half of the costals there are seven or
eight ridges, and the remaining surface of the costals and neurals are
rugose. The marginals lack ridges, and the posterolateral marginals are
not serrated. The anterior end of the carapace has a broad shallow
notch. The first neural is rounded, and the 2d, 3d, and 4th are
hexagonal, with the broad ends forward. Anterior margins of the 2d and
3d neurals are concave, and the anterior margin of the 4th neural is
straight.
The sulci bounding the scutes are moderately impressed. The width of the
first vertebral scute, anteriorly and posteriorly, is less than the
width of the second vertebral scute. The costal scutes join the marginal
scutes on the marginal plates.
The plastron, broadly indented at the posterior end, does not have the
posterior lobe flared laterally as it is in Recent species of
_Chrysemys_, and lacks any pronounced notch at the femoro-anal suture.
The humero-pectoral sulcus crosses the plastron behind the entoplastron
in a straight line, and reaches the border anterior to the axillary
notch. The pectoro-abdominal suture is anteriorly convex at the sides
and concave at the midline.
A comparison of this carapace and plastron with a series of specimens of
Recent _Chrysemys picta_ and _Pseudemys scripta_ of approximately the
same size reveals characters indicated in the following chart:
==================================================================
RECENT _Chrysemys_ | _Chrysemys limnodytes_ | RECENT _Pseudemys_
--------------------+------------------------+--------------------
Not serrated. | Posterolateral | Serrated.
| marginals not serrated.|
--------------------+------------------------+--------------------
Not notched. | Carapace with broad | Notched.
| shallow notch at |
| anterior end. |
--------------------+------------------------+--------------------
Occasional faint | Plastron does not have | Distinct notch at
notch at femoro-anal| a pronounced notch at | femoro-anal suture.
suture. | femoro-anal suture. |
--------------------+------------------------+--------------------
Posterior lobe of | Posterior lobe of | Posterior lobe of
plastron flares | plastron does not | plastron does not
laterally. | flare laterally. | flare laterally.
--------------------+------------------------+--------------------
Carapace smooth. | Carapace has smooth | Carapace has
| contours. | depressions and
| | elevations.
--------------------+------------------------+--------------------
Old specimens | Seven or eight ridges | Ridges cover
occasionally have | on lower half of | costals.
five or six ridges | costals. |
near border of | Remaining surface of |
costals. | costals and neurals |
| rugose. |
--------------------+------------------------+--------------------
No ridges on | No ridges on | May or may not
marginals. | marginals. | have ridges on
| | marginals.
--------------------+------------------------+--------------------
Nuchal smooth. | Nuchal smooth. | Nuchal has ridges.
--------------------+------------------------+--------------------
Carapace not | Probably arched less | Greatly arched.
greatly arched. | than in _Pseudemys_, |
| but more than in any |
| Recent _Chrysemys_. |
--------------------+------------------------+--------------------
Keel often present | No keel present. | Keel often present.
at birth, but soon | |
lost. | |
--------------------+------------------------+--------------------
Anterior and | Anterior and posterior | Anterior width of
posterior widths of | widths of first | first vertebral
first vertebral | vertebral scute less | scute less than
scute approximately | than width of second | posterior width,
same as width of | vertebral scute. | or both dimensions
second vertebral | | less than width of
scute. | | second vertebral
| | scute.
--------------------+------------------------+--------------------
Ribs do not tend | Ribs not prominent on | Ribs tend to be
to be prominent on | costals. | prominent on
costals. | | costals.
--------------------+------------------------+--------------------
Hay attached considerable taxonomic importance to the characters of the
nuchal and I find its characters to be fairly constant in the specimens
of Emydidae examined. Although the nuchal of _Chrysemys limnodytes_ is
incomplete, it can be distinguished from the nuchals described by Hay as
types of his several fossil Emydids. Differences in the nuchal, together
with those in the carapace and plastron, serve to distinguish the
species from other genera of the Emydidae.
When the specimen is compared with _Chrysemys timida_ Hay, of the
Nebraska Pleistocene, many similarities, mostly of generic rank, are
seen. _Chrysemys limnodytes_ is broader in relation to length than is
either _C. timida_ or any Recent specimen examined of the same size. The
greatest allowance possible in estimating the length of _C. limnodytes_
fails to bring the ratio of its breadth to length within the range of
Recent specimens of similar size. Data from 96 specimens of Recent
_Chrysemys picta_ show that the ratio of length to width is not affected
by sex, but that the ratio does vary with the age of the specimen. In
young animals the length and width are approximately equal, but with
further growth the length becomes relatively greater. Specimens in the
length group of 135 to 144 mm. have the widths ranging from 71 to 81 per
cent of the lengths. In all specimens larger than this, the ratio is in
the low seventies, and the largest specimen, 177 mm. in length, has the
width of the carapace amounting to only 74 per cent of the length. The
fossil species, _C. timida_, with a length of 160 mm., has the width
amounting to 75 per cent of the length, and _C. limnodytes_, with an
estimated length of 180 mm., has the width amounting to 80.5 per cent of
the length. _C. timida_ is widest anteriorly, whereas _C. limnodytes_
and the other species of the genus are widest posteriorly. Less obvious
differences between the two fossils are the narrower anterior margin of
the nuchal, the concave anterior end of the carapace, the sculptured
surface of the carapace, and the relatively wider neurals and longer
vertebrals of _C. limnodytes_.
DIMENSIONS OF THE TYPE SPECIMEN
(In millimeters)
Total length of carapace, 180 (estimated); greatest width of carapace,
145 (estimated); height of carapace, more than 50.
Length of plastron, 165 (estimated); width of plastron, 130 (estimated);
length of anterior lobe, 45 (estimated); width of anterior lobe, 75
(estimated); length of posterior lobe, 62; width of posterior lobe, 82;
length of bridge from axillary to inguinal notch, 60.
PLATES OF THE CARAPACE AND PLASTRON
Nuchal: Width of anterior margin, 12 (estimated); greatest width, 37
(estimated); length at midline, 35 (estimated).
First neural: Greatest width, 13; length at midline, 17. Second neural:
Greatest width, 16; length at midline, 14. Third neural: Greatest width,
18; length at midline, 16. Fourth neural: Greatest width, 18; length at
midline, 16.
Costals: Thickness at proximal end, 3-5; thickness at distal end, 2.
First costal: Length of margin bordering nuchal, 23 (this and the
following measurements of the costal and marginal plates are of plates
from the right side of the animal except those indicated by an "L");
length of margin bordering neurals, 17; length of margin bordering
marginals, 38; length of margin bordering 2d costal, 51. Second costal:
Length of margin bordering 1st costal, 53; length of margin bordering
neurals, 16; length of margin bordering marginals, 25; length of margin
bordering 3d costal, 56. Third costal: Length of margin bordering 2d
costal, 55 (L), 56; length of margin bordering neurals, 19; length of
margin bordering marginals, 18; length of margin bordering 4th costal,
58. Fourth costal: Length of margin bordering 3d costal, 58; length of
margin bordering neurals, 16; length of margin bordering marginals, 22;
length of margin bordering 5th costal, 55. Fifth costal: Length of
margin bordering 4th costal, 52; length of margin bordering neurals, 16;
length of margin bordering marginals, 20; length of margin bordering 6th
costal, 41.
First marginal: Length of margin bordering nuchal, 23 (L), 21; length of
outer margin, 23 (L), 23; length of inner margin, 12 (L), 12; length of
margin bordering 2d marginal, 22 (L), 21. Second marginal: Length of
margin bordering 1st marginal, 22 (L); length of outer margin, 22 (L);
length of inner margin, 15 (L); length of margin bordering 3d marginal,
16 (L). Seventh marginal: Length of margin bordering 6th marginal, 18
(L), 17 (estimated); length of outer margin, 25 (L), 23 (estimated);
length of inner margin, 18 (L), 18; length of margin bordering 8th
marginal, 22 (L), 22. Eighth marginal: Length of margin bordering 7th
marginal, 22 (L), 23; length of outer margin, 22 (estimate of L), 22;
length of inner margin, 18 (L), 18; length of margin bordering 9th
marginal, 24 (estimate of L), 23. Ninth marginal: Length of margin
bordering 8th marginal, 24 (L); length of outer margin, 20 (L), 19;
length of inner margin, 19 (L); length of margin bordering 10th
marginal, 23 (L), 23. Eleventh marginal: Length of margin bordering 10th
marginal, 22 (L); length of outer margin, 16 (L); length of inner
margin, 12 (L); length of margin bordering pygal, 18 (L).
Entoplastron: Width, 24 (estimated).
Hyoplastron: Length of margin bordering epiplastron, 25; length of
margin on midline, 37; length from junction of epiplastronal border and
outer border to point on posterior border equidistant from midline, 53;
width from midline to axillary notch, 39; distance between axillary
notch and posterior border, 31.
Hypoplastron: Length of margin bordering midline, 42; length of
posterior (xiphiplastronal) margin, 40; distance from junction of
xiphiplastronal margin and outer margin to point on anterior border
equidistant from midline, 49 (estimated); distance between inguinal
notch and anterior border, 29.
Xiphiplastron: Length of anterior (hypoplastronal) margin, 38; length of
margin along midline, 43; distance from extreme posterior extension of
xiphiplastron to midline, 14.
SCUTES OF CARAPACE AND PLASTRON
First marginal scute: Length of margin bordering 2d marginal, 15 (L),
14; length of anterior margin, 15 (L); length of posterior margin, 14
(L); length of inner margin, 13 (L); length of outer margin, 23 (L).
Third marginal scute: Length of anterior margin, 14 (L). Eighth marginal
scute: Length of anterior margin, 15 (L), 15; length of posterior
margin, 16 (estimate of L), 16; length of inner margin, 20 (L), 20;
length of outer margin, 25 (estimate of L), 25. Ninth marginal scute:
Length of anterior margin, 17 (L), 16; length of posterior margin, 17
(L), 17; length of inner margin, 18 (L), 20; length of outer margin, 21
(L), 21. Tenth marginal scute: Length of anterior margin, 17 (L), 17.
Eleventh marginal scute: Length of posterior margin, 14 (L).
First costal scute: Length of margin bordering vertebrals, 45. Second
costal scute: Length of margin bordering vertebrals, 35 (L), 35; length
of margin bordering 3d costal scute, 52.
First vertebral scute: Length of anterior margin, 24 (estimated);
greatest width, 32 (estimated); length at midline, 35 (estimated).
Second vertebral scute: Length of anterior margin, 27; greatest width,
42; length at midline, 29. Third vertebral scute: Length of anterior
margin, 33; greatest width, 42; length at midline, 40 (estimated).
Pectoral scute: Length of humero-pectoral sulcus from midline to outer
border, 38; length of margin of pectoral scute on midline, 18; distance
between junction of humero-pectoral sulcus and outer border and point
on pectoro-abdominal sulcus equidistant from midline, 19; distance from
axillary notch to point on pectoro-abdominal sulcus equidistant from
midline, 17.
Abdominal scute: Length of margin of scute on midline, 43; width of
posterior border of abdominal scute from midline to inguinal notch, 41;
distance from inguinal notch to a point on pectoro-abdominal sulcus
equidistant from midline, 44.
Femoral scute: Length of border of scute on midline, 24; width of
anterior border of scute from midline to inguinal notch, 41; width of
posterior border of scute from midline to outer border (along sulcus),
40; length of outer margin of scute from inguinal notch to femoro-anal
sulcus, 46.
Anal scute: Length of margin at midline, 36; length of femoro-anal
sulcus, 40.
_Remarks._--Noteworthy is the intermediate nature of _C. limnodytes_
when compared with species of the genera _Chrysemys_ and _Pseudemys_.
However, any resemblance to _Pseudemys_ is not to be considered as
evidence that _C. limnodytes_ is in any way ancestral to the genus
_Pseudemys_. The fossil specimens of _Pseudemys_ from the Pliocene are
too poorly known to allow the student certainly to place them in their
correct systematic positions. The fossil Emydids from Western Europe,
listed as species of _Chrysemys_, differ very much from this species, or
belong to other genera of the family.
Only a few turtles are known from the Laverne formation. Hesse (Chaney
and Elias, 1936) reported a small _Testudo_ from the Laverne of Beaver
County, Oklahoma, but neglected to state whether it was among the
material borrowed by him from the University of Kansas Museum of Natural
History. The Museum has an incomplete carapace and plastron (No. 3101)
of a small _Testudo_ from that locality and formation. In Harper County,
Oklahoma, the field party from the University recovered a large number
of fragments of a large _Testudo_. Although this specimen is as yet
unprepared, enough fragments have been pieced together to reveal that
the tibia is 127 mm. long. This dimension and those of some of the
fragments indicate that the animal may have been four to five feet long.
Mrs. Bernita Mansfield of the Geology Department, University of Kansas,
prepared the plate.
LITERATURE CITED
BERGOUNIOUX, FREDERIC-MARIE.
1935. Contribution a l'étude paléontoligique des chéloniens:
Chéloniens fossiles du Bassin d'Aquitaine. Memoires de la
Société géologique de France, vol. 11, Mem. 25, pp. 1-215,
44 figs., 16 pls.
1937. Relations fauniques entre des chélonien fossiles de l'Espagne
et de la France. Comptes Rendus Acad. Sci. Paris, vol. 204,
pp. 793-795.
1938. Chéloniens fossiles d'Espagne. Bulletin de la Societe
d'histoire Naturelle de Toulouse, vol. 72, pp. 257-288,
7 figs.
CHANEY, R. W., and ELIAS, M. K.
1936. Late Tertiary Floras from the High Plains, with a Chapter
on the Lower Pliocene Vertebrate Fossils from the Ogallala
Formation (Lavern Zone) of Beaver County, Oklahoma, by
Curtis J. Hesse. Publ. Carnegie Inst. Wash., No. 476,
pp. 1-72, 11 figs., 7 pls.
FRYE, J. C., and HIBBARD, C. W.
1941. Pliocene and Pleistocene Stratigraphy and Paleontology of
the Meade Basin, Southwestern Kansas. University of Kansas
Publications, State Geological Survey of Kansas, Bulletin 38,
pp. 389-424, 3 figs., 4 pls.
HAY, O. P.
1908. The Fossil Turtles of North America. Publ. Carnegie Inst.
Wash., No. 75, pp. i-iv, 1-568, 704 figs., 113 pls.
_Transmitted March 1, 1948._
22-3340
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