_Chicot_: Lake Chicot. _Clark_: Terre Noir Creek, 13 mi. W
Arkadelphia. _Garland_: Ouachita River, Mountain Pine (Conant and
Goin, 1948:7). _Hempstead_: _Jefferson_: (Dowling, _loc. cit._).
_Lawrence_: Black Rock (Dellinger and Black, 1938:46). _Madison_:
_Scott_: _St. Francis_: (Dowling, _loc. cit._). _Washington_: near
Greenland (Dellinger and Black, _loc. cit._).
COLORADO: _Boulder_: Boulder Creek, E Boulder; Boulder Creek, 6 mi. S
and 1 mi. E Longmont. _Larimer_: Cache la Poudre River. _Logan_: 8 mi.
NE Sterling. _Morgan_: Platte River "near" Fort Morgan. _Otero_:
Purgatoire River at Higbee. _Prowers_: Arkansas River at Lamar.
_Weld_: Poudre River "near" Greeley; Evans. _Yuma_: Bonny Dam,
Republican River (Maslin, 1959:24-25).
IOWA: _Dickinson_: Little Sioux River, Okoboji Twp. (Blanchard,
1923:24). _Story_: Skunk River, 5 mi. NNE Ames (Conant and Goin,
1948:9).
KANSAS: _Allen_: Petrolia (KKA). _Barber_: 7 mi. S Sun City. _Butler_:
3 mi. SE Augusta (Burt and Hoyle, 1934:198). _Chase_: 10 mi. SW Olpe;
7 mi. SW Saffordville (Breukelman and Smith, 1946:112). _Cherokee_:
tributary of Spring River, 1 mi. N Riverton (Hall and Smith,
1947:451). _Coffey_: (Smith, 1956:160, symbol on map). _Cowley_: 11
mi. SE Winfield (Stejneger, 1944:55). _Crawford_: Pittsburg (Hall and
Smith, _loc. cit._). _Doniphan_: "near" Geary (Linsdale, 1927:81).
_Elk_: (Smith, _loc. cit._). _Ellis_: Big Creek (Brennan, 1934:190);
Ellis (Conant and Goin, 1948:2). _Franklin_: Middle Creek, SE part of
county (Gloyd, 1928:135). _Greenwood_: (Stejneger, _op. cit._:54).
_Leavenworth_: Missouri River "near" Fort Leavenworth (Brumwell,
1951:208). _Lyon_: 5 mi. E Emporia (Breukelman and Smith, _loc.
cit._). _Marion_: (Smith, _loc. cit._). _Meade_: Meade County State
Park, _ca._ 13 mi. SW Meade (Tihen and Sprague, 1939:505). _Ness_:
5.5 mi. NW Ness (Breukelman and Smith, _loc. cit._). _Osage_: Marais
des Cygnes River; Long and Jordan Creeks (Clarke, 1958:21). _Reno_: 6
mi. E Turon. _Sedgwick_: 2 mi. NE Cheney (Burt, 1935:321). _Sheridan_:
State Lake 7 mi. NE Quinter, Gove County (Breukelman and Smith, _loc.
cit._). _Wabaunsee_: Dragoon Creek at Harveyville (Clarke, 1956:215).
_Wallace_: (Burt, 1933:208). _Wilson_: Fall River, 1/2 mi. S Neodesha
(Clarke, _loc. cit._).
MINNESOTA: _Anoka_: _Benton_: _Chisago_: (Breckenridge, 1944:184,
symbols on map). _Crow Wing_: (Breckenridge, _op. cit._:185).
_Dakota_: (Hedrick and Holmes, 1956:126). _Goodhue_: (Breckenridge,
_op. cit._:184, symbol on map). _Hennepin_: Minneapolis; Lake
Minnetonka (Breckenridge, _op. cit._:187); 5 mi. N. Minneapolis
(Breckenridge, 1955:5). _Houston_: Root River near Hokah. _Lesueur_:
Lake Washington (Hedrick and Holmes, _loc. cit._). _Meeker_: Swan Lake
(Breckenridge, 1957:232). _Pine_: (Breckenridge, 1944:185). _Ramsey_:
_Rice_: _Sherburne_: _Stearns_: (Breckenridge, _op. cit._:184, symbols
on map). _Washington_: just north of Stillwater (Hedrick and Holmes,
_loc. cit._). _Winona_: Winona (Breckenridge, _op. cit._:187). _Yellow
Medicine_: (Breckenridge, _op. cit._:185). _County unknown_ (Goodhue
or Wabasha): Lake Pepin (Breckenridge, _op. cit._:184).
MISSOURI: _Boone_: east of Ashland (Henning, 1938:92). _Jackson_:
Missouri River "near" Atherton (Anderson, 1942:219). _Jefferson_:
Mississippi River "near" mouth Glaize Creek at Sulphur Springs; Glaize
Creek at Barnhart (Boyer and Heinze, 1934:199). _St. Clair_: Osage
River "near" Osceola. _Vernon_: Marmaton River, 7 mi. N Moundville
(Conant and Goin, 1948:9).
MONTANA: Yellowstone River (Conant and Goin, 1948:9).
NEBRASKA: _Adams_: 1 mi. N Ayr (Hudson, 1942:101). _Dawson_: 2 mi. SE
Gothenburg (Gehlbach and Collette, 1959:142). _Franklin_: 2 mi. SW
Naponee. _Gage_: 1 mi. W Barnston. _Hitchcock_: 3 mi. E Stratton.
_Holt_: Elkhorn River "near" Atkinson. _Lancaster_: Lincoln (Hudson,
_loc. cit._). _Lincoln_: 1 mi. S Sutherland (Gehlbach and Collette,
_loc. cit._). _Red Willow_: 14 mi. NW McCook. _Richardson_: 2 mi. S
Rulo. _Wheeler_: 2 mi. W Ericson (Hudson, _loc. cit._).
OKLAHOMA: _LeFlore_: Wister (Conant and Goin, 1948:9); Shady Pointe
(KKA); Poteau River, 6.5 mi. W Heavener (Trowbridge, 1937:301).
_Tulsa_: Arkansas River "near" Tulsa (Force, 1930:38).
WYOMING: _Goshen_: Platte River (Conant and Goin, 1948:10).
=Trionyx spinifer asper= (Agassiz)
Gulf Coast Spiny Softshell
Plates 37 and 38
_Aspidonectes asper_ Agassiz, Contr. Nat. Hist. United States,
1(Pt. 2):405; 2(Pt. 3):pl. 6, fig. 3, 1857.
_Trionyx spinifer asper_ Schwartz, Charleston Mus. Leaflet,
No. 26:17, pls. 1-3, map 2, May, 1956.
_Platypeltis agassizii_ Baur, Amer. Nat., 22:1121, 1888.
_Type._--Lectotype, MCZ 1597; alcoholic female; locality designated as
Pearl River, Columbus, Marion County, Mississippi; received from Mr.
Winthrop Sargent of Natchez, Mississippi.
_Range._--Southeastern United States except peninsular Florida from
the Florida Parishes of Louisiana east to southern North Carolina;
Gulf Coast drainage including that of Lake Pontchartrain, Louisiana,
eastward to the Apalachicola River system, and Atlantic Coast drainage
including that of the Altamaha River in Georgia northward to the Pee
Dee River drainage in South Carolina (see map, Fig 19).
_Diagnosis._--Juvenal pattern of black ocelli and spots, and two or
more black, interrupted, lines paralleling rear margin of carapace;
pale postocular and postlabial stripes often united on side of head;
length of plastron short.
_Description._--Plastral length of smallest hatchling, 2.9 centimeters
(USNM 134244); of largest male, 13.2 centimeters (TU 17117); of
largest female, 27.0 centimeters (TU 13474).
Blackish marginal rings on carapace number two, three or four
posteriorly, but decrease in number anteriorly; segments of marginal
rings may extend to nuchal region; marginal rings increasingly
interrupted inwardly; pattern of hatchlings having well-defined
marginal rings that are not extensively interrupted (often males), or
having marginal rings broken into small segments or series of dots,
and pale outer margin of carapace marked by ill-defined, hazy, inner
border (often females); conspicuous marginal rings often lacking on
hatchling females; pale rim of carapace not four or five times wider
posteriorly than laterally; carapace having blackish dots, spots,
small ocelli or a combination thereof; marks on carapace of slightly
varying sizes, some occasionally barlike (usually males); some
hatchling females showing pale, irregular blotching on carapace, often
characterized by small lichenlike figures superimposed on blackish
dots.
Striping on snout variable; pale, dark-bordered stripes usually unite
in front of eyes and form right or acute angle; medial dark borders of
pale stripes on snout not joined anteriorly, broken into segments or
dots, reduced to single median line, united to form straight line
connecting anterior margins of orbits (usually with slight medial
indentation), or absent; pale postocular and postlabial stripes often
joined, relationship variable and on either side of head; side of head
with or without dark markings, sometimes a pale subocular blotch
bordered below by a dark line; pattern on dorsal portions of soft
parts of body contrasting, less so on limbs of hatchlings; pattern of
irregular dark marks, dark streaks usually coincident with digits;
longitudinal streaks often occur on neck; elongate tail of adult males
usually having well-defined, dorsolateral, pale bands with dark lower
border more diffuse than upper border.
Underparts whitish often with dusky markings on rear of carapace or in
region of bridge; blackish marks often on webbing and portions of
soles and palms, and chin and throat.
Small conical tubercles along anterior edge of carapace on adult
males; remnants of juvenal pattern usually present on carapace of
large females; conical or knoblike tubercles on anterior edge of
carapace of large females; accessory knoblike tubercles in nuchal
region (a paravertebral pair usually most prominent), and posteriorly
in middle of carapace on large females.
Ontogenetic variation in PL/HW, mean PL/HW of specimens having
plastral lengths 7.0 centimeters or less, 3.87, and exceeding 7.0
centimeters, 4.94; ontogenetic variation in CL/CW, mean CL/CW of
specimens having plastral lengths 8.5 centimeters or less, 1.11, and
exceeding 8.5 centimeters, 1.16; mean CL/PCW, 1.71; mean CL/PL, 1.45.
_Variation._--The sex of some hatchlings can be distinguished by the
pattern on the carapace (see Plate 37 for different patterns), but the
sex of many hatchlings cannot be distinguished on the basis of
pattern.
In the early stages of this study, I thought that the pattern on the
carapace differed in eastern and western populations, and that the
zone of intergradation was in Alabama. Adult males from the
Tombigbee-Alabama river drainage and westward were noted to have
blackish spots (some slightly ocellate) intermixed with few, if any,
smaller blackish dots, whereas the adult males from east of the
Tombigbee-Alabama river drainage had many small, black dots intermixed
with slightly larger, mostly ocellate marks (see Plate 38, left, top
and bottom, for contrast); also, hatchlings from western populations
were never observed to have four marginal rings. On the basis of
pattern, I would have thought that the individual having many ocelli,
that lacks correct locality data and that is photographed by Stejneger
(1944:Pl. 26), came from Georgia or South Carolina; but, the pattern
(_op. cit._:Pl. 27) of a specimen, probably an adult male, from South
Carolina, resembles the pattern on adult males from Louisiana. The
differences noted above are probably due to individual variation
rather than geographic variation.
Color notes taken from life of a freshly-killed adult male (TU 16071,
Louisiana) are: carapace olive, spots blackish, outer rim buff; top of
head olive, postocular and postlabial stripes yellow with blackish
borders, stripes on snout buff with blackish borders; dorsal ground
color of soft parts of body pale olive-green, larger marks blackish,
ground color laterally toward juncture of pattern and immaculate
undersurface, and toward insertions of neck and limbs becoming
yellowish; webbing on hind limbs having reddish tinge; dorsolateral
bands on tail yellow with blackish borders; undersurface whitish; chin
and throat olive-green with blackish marks; becoming buff then whitish
posteriorly.
[Illustration: FIG. 20. Basicranial length and ratio of greatest
diameter of internal choanae to least width of maxillary
bridge (IC/MB) on 30 skulls of _T. ferox_ (open circles),
26 of _T. spinifer_ (crosses), and 12 of the _agassizi_-form
(solid circles; half shaded circle represents holotype of
_agassizi_). Skulls of the _agassizi_-form tend to have
slightly smaller internal choanae than those of _spinifer_
or _ferox_.]
Occasional specimens have only one definite dark line paralleling the
rear margin of the carapace. Schwartz (1956:16) reported that
Charleston Museum No. 55.159.26 has only one solid line at the margin
of the carapace, and I received an adult male (KU 47120) reported to
have come from the Pearl River that is aberrant in not having more
than one dark marginal line. USNM 95191, a large stuffed female from
the Pearl River is mentioned by Stejneger (1944:59, Pl. 17) as having
marks that "assume the form of short lines parallel with the
submarginal ring"; I examined this specimen and noted that it had only
one dark marginal line. Stejneger (_op. cit._:64) mentioned another
from the Pearl River drainage, and Crenshaw and Hopkins (1955:20)
wrote that some individuals from Georgia have only one dark marginal
line. Presumably MCZ 1606 (now in the Albany Museum) recorded by
Stejneger (_op. cit._:52) as _Amyda s. spinifer_ from Columbus,
Georgia, is another specimen.
[Illustration: FIG. 21. Basicranial length and greatest width of
alveolar surface of maxilla on 52 skulls of _T. spinifer_ (open
circles) and 11 of the _agassizi_-form (solid circles; half shaded
circle represents holotype of _agassizi_). Most skulls of the
_agassizi_-form that exceed 43 mm. in basicranial length have a
more expanded, alveolar surface of the maxilla than skulls of
_spinifer_ of approximately the same size. All skulls exceeding
50 mm. are those of females.]
Some skulls of soft-shelled turtles from streams of the Atlantic Coast
drainage, including the skull of the holotype of _Platypeltis_ (=
_Trionyx_) _agassizi_ Baur (MCZ 37172, Pl. 54), show at least two
differences from other skulls of _asper_ and from those of other
subspecies of _T. spinifer_. Figure 20 shows that skulls of _agassizi_
tend to have slightly smaller internal choanae (ratio IC/MB) than
those of _T. spinifer_ and _T. ferox_; there is seemingly little
difference between skulls of _ferox_ and _spinifer_, and little, if
any, ontogenetic variation. Figure 21 shows that most skulls of the
_agassizi_-form that exceed 43.0 millimeters have a more expanded,
alveolar surface of the maxilla than skulls of _spinifer_ of
approximately the same size; most skulls exceeding a basicranial
length of 43.0 millimeters, and certainly all skulls exceeding 50.0
millimeters are those of females. Stejneger (1944:Pl. 30) also has
provided photographs of a skull of the _agassizi_-form. It is of
interest that of the 12 _agassizi_-form skulls (MCZ 37172; USNM 8708,
029034, 51981, 66859, 71681, 91282, 91310-11, 92521, 92583-84) that I
examined some resemble _ferox_ (Neill, 1951:9) in having the alveolar
surfaces of the jaws broadened, and the greatest width at the level of
the quadratojugal (Table 3, Plate 54); also, the localities of all 12
skulls are within the geographic range of _ferox_. Skulls of _ferox_,
however, have conspicuously broadened alveolar surfaces of the jaws
only when they exceed in length the largest skulls of _agassizi_. The
differences of skulls of the _agassizi_-form possibly reflect
isolation in the Atlantic Coast drainage, and an adaptation in feeding
habits. So far as I can ascertain, individuals occurring in rivers of
the Atlantic Coast drainage in Georgia and South Carolina (referable
to _agassizi_) do not differ consistently in external characters from
individuals of _T. s. asper_ that occur westward in the Apalachicola
drainage.
_Comparisons._--_Trionyx s. asper_ can be distinguished from all other
subspecies of _T. spinifer_ by usually having more than one black line
paralleling the rear margin of the carapace. This character and the
frequent fusion of the postlabial and postocular stripes on the side of
the head distinguish _asper_ from _spinifer_ and _hartwegi_. _T. s.
asper_ differs from _pallidus_, _guadalupensis_ and _emoryi_ in having
blackish spots and ocelli on the carapace, and lacking whitish dots or
tubercles. _T. s. asper_ resembles _spinifer_, _hartwegi_ and _pallidus_
but differs from _guadalupensis_ and _emoryi_ in having conical
tubercles along the anterior edge of the carapace in large females. For
additional differences see accounts of other subspecies.
Of the subspecies of _T. spinifer_, _asper_ has a proportionately wide
head that is closely approached in the subspecies _guadalupensis_ and
_emoryi_; _T. s. asper_ differs from _guadalupensis_ and _emoryi_ in
having a wider carapace, and resembles _hartwegi_ and _spinifer_, but
differs from the other subspecies in having the carapace widest at a
plane approximately one-half way back on the carapace. _T. s. asper_
differs from the other subspecies in having the shortest plastron.
_Remarks._--Stejneger (1944:72-74) has discussed the history of Baur's
_Platypeltis agassizi_. Briefly, Agassiz's description of _Platypeltis
ferox_ wherein he (1857:402) states that "The young ferox [Pl. 6, fig.
3] has two or three concentric black lines separating the pale margin
...," was applicable to _T. s. asper_. Agassiz mentioned also that the
young of his _Aspidonectes asper_ (_op. cit._:406) "as in Platypeltis
ferox, ... has ... two or three black lines separating the pale rim of
the posterior margin, ..."; however, _A. asper_ was distinguished
chiefly by the "... prominent warts of the bony plates (_loc. cit._)."
Because the description of the pattern of _ferox_ resembled that of
_asper_, the validity of _asper_ was not agreed upon by all workers.
Boulenger (1889:245, footnote 1) referred to _asper_ as a species that
required "... further investigation."
Baur (1888:1121) realized that Agassiz's description of _ferox_ was not
that of _Testudo ferox_ Schneider, and regarded the description of
Agassiz as applying to a new species, which he named _Platypeltis
agassizii_; Baur (_op. cit._:1122) also recognized _asper_, referring it
to the genus _Aspidonectes_. Baur designated a specimen from Georgia
(the only individual seen by him) as the type of _agassizi_ (Stejneger,
_op. cit._:73, footnote); this specimen is now MCZ 37172. Five years
later (1893:218), Baur discussed generic relationships of trionychids,
seemingly only on the basis of skulls (holotype of _agassizi_ not
mentioned), and referred _agassizi_ to the resurrected genus
_Pelodiscus_ Fitzinger, 1835, which was distinguished from the other two
American genera that Baur recognized (_Platypeltis_ and _Amyda_) by
having the "Posterior nares reduced in size by the inner and posterior
extension of the maxillaries." Baur also transferred _asper_ to the
genus _Platypeltis_, and restricted the type locality of that species to
"Lake Concordia, La." (_op. cit._:220); the type locality of _agassizi_
was restricted to "Western Georgia" (_loc. cit._).
The name-combination, _Pelodiscus agassizi_, was not generally accepted.
Hay (1892:144) and Siebenrock (1924:188) referred _agassizi_ to the
genus _Trionyx_. Hay regarded _agassizi_ as a full species (see
discussion by Stejneger, 1944:73), whereas Siebenrock considered it a
subspecies of _spiniferus_; both authors regarded _asper_ as a synonym
of _agassizi_. Neither _asper_ nor _agassizi_ was mentioned in the first
three editions of the Check List of North American Amphibians and
Reptiles (Stejneger and Barbour, 1917, 1923, 1933); the same authors in
the fourth (1939:171, 172) and fifth editions (1943:212, 213) listed
_agassizi_ as a full species, and _asper_ as a subspecies of
_spinifera_. Stejneger (1944) used the same arrangement as set forth in
the fourth and fifth editions of the Check List, and distinguished
_agassizi_ on the basis of cranial characters, namely, the small size of
the internal choanae, the greater width of the alveolar surface of the
lower jaw, and the position of the suture between the palatine and
basisphenoid relative to the posterior edge of the temporal fossa. Neill
(1951:9) regarded the peculiarities of the _agassizi_-type skull as
inconstant, but recognized _agassizi_ (and _asper_) as a subspecies of
_ferox_. Crenshaw and Hopkins (1955) showed that _asper_ did not
intergrade with _ferox_. Schwartz showed that _agassizi_ did not
intergrade with _ferox_, and regarded _agassizi_ as a synonym of _T. s.
asper_ (1956:17), but stated that _agassizi_ possessed "wider crushing
surfaces on the maxillae than does _T. s. asper_, even when skulls of
the same size and sex are compared" (_op. cit._:9).
The holotype of _Platypeltis agassizi_ (MCZ 37172) is a dried adult
female consisting of shell, skull and limb bones; the carapace is
approximately 300 millimeters long (Schwartz, _loc. cit._). I have
examined only the skull of MCZ 37172 (Plate 54), and it is the largest
of 12 _agassizi_-type skulls I have seen. The basicranial length is 72.5
millimeters, and the greatest width, which occurs at the level of the
quadratojugals, is 52.9 millimeters. The _agassizi_-type skulls have
been discussed under the subsection on variation.
The type locality of _T. s. asper_, Lake Concordia, Louisiana (lower
Mississippi River drainage) as restricted by Baur (1893:220), is in an
area of intergradation of three subspecies of _Trionyx spinifer_ where
most individuals are not typical of _asper_. The syntypes, the
designation of MCZ 1597 as a lectotype, and Pearl River, Columbus,
Marion County, Mississippi, as the type locality have been discussed
elsewhere (Webb, 1960).
The range of _T. s. asper_ overlaps that of _T. ferox_ in Georgia and
South Carolina. The two species remain distinct in the area of overlap
of their geographic ranges (Crenshaw and Hopkins, 1955:16; Schwartz,
_op. cit._:5). _Trionyx s. asper_ intergrades with _T. s. hartwegi_ and
_T. s. spinifer_ in the lower Mississippi Valley (Conant and Goin,
1948:11).
However, there are few specimens available that indicate intergradation
of _asper_ with the _spinifer-hartwegi_ complex in the lower Mississippi
River drainage; this may be due to the fact that _asper_ inhabits
waterways that do not drain into the Mississippi River. Perhaps
intergradation is more prevalent than the morphological basis that I
have relied upon indicates; in any event, there are few specimens that
have more than one dark marginal line (which is the only character that
is unique for _asper_) from the lower Mississippi drainage. A young male
(TU 11928.9) from Bayou Gauche between Paradis and Des Allemands, St.
Charles Parish, Louisiana, has a pattern on the carapace resembling that
of _asper_; several other small softshells (TU) are available from the
same locality but none shows more than one dark marginal line. Another
specimen (USNM 95192), a young female from a barrow pit of the Big Black
River (Mississippi River drainage), Madison County, Mississippi,
resembles _asper_ in having more than one marginal ring. Of three large
females from Moon Lake, an ox-bow of the Mississippi River in Coatopa
County, Mississippi (AMNH 5285-86, 5289), only 5289 shows evidence of
two marginal lines. USNM 73669 (Greenwood, LeFlore County, Mississippi)
also indicates intergradation in that the spots tend to be linear just
inside the dark marginal line, but the specimen more closely resembles
the _hartwegi-spinifer_ complex rather than _asper_.
There seems to be little adumbration of the dark marginal lines of
_asper_ in populations from the lower Mississippi River drainage.
Blackish spots and ocelli vary in size and there are many kinds of
pattern on the carapace. Soft-shelled turtles inhabiting the Mississippi
River and its tributaries in Louisiana and Mississippi certainly
represent an intergrading population of _spinifer_ and _hartwegi_, and,
to a lesser extent, of _asper_. Soft-shelled turtles inhabiting the
Pearl River drainage and rivers that drain into Lake Pontchartrain
immediately adjacent to the east are predominantly _asper_.
Specimens having localities from the Pearl River and Lake Pontchartrain
drainages are listed under the account of _asper_ and are referred to
that subspecies on the distribution map; specimens from the Mississippi
drainage in Mississippi are referred to _spinifer_.
One specimen (UMMZ 59198, Bradley County, Tennessee), from the Tennessee
River drainage where _T. s. spinifer_ occurs, deviates markedly from
_spinifer_ and suggests intergradation. UMMZ 59198, plastral length 4.8
centimeters, has ocelli in the center of the carapace only two
millimeters in diameter, a distinct but interrupted, second marginal
ring consisting of spots, and the pale postlabial and postocular stripes
in contact on both sides of the head.