Table Of ContentPROC. BIOL. SOC. WASH.
107(4), 1994, pp. 729-737
TWO NEW SPECIES AND ONE NEW COMBINATION
OF FRESHWATER CRABS FROM MEXICO
(CRUSTACEA: BRACHYURA: PSEUDOTHELPHUSIDAE)
Fernando Alvarez and Jose Luis Villalobos
Abstract.—Pseudothelphusa guerreroensis Rathbun, 1933, is referred to the
genus Tehuana Rodriguez & Smalley, 1969, based on the morphology ofthe
first gonopod, with a lobular marginal process partially fused to the mesial
process, and the presence ofa distinct superior frontal border ofthe carapace,
both traits characteristic ofTehuana. Two new species, Tehuana lamotheiand
Pseudothelphusa nayaritae, are described from the Mexican States ofChiapas
and Nayarit, respectively. Tehuana lamothei was collected 230 km southeast
ofthepresent southernmostlimit ofthegenus. Tehuana lamotheiisrecognized
by a gonopod with the most reduced mesial process ofall ofthe species in the
genus. Pseudothelphusa nayaritae belongs to a group ofspecies from western
Mexico which lacks a marginal process on the first gonopod.
Two specimens ofPseudothelphusa gue- OdontothelphusaRodriguez, 1982;Epithel-
rreroensis Rathbun, 1933, deposited in the phusa Rodriguez & Smalley, 1969; and
&
Crustacean Collection, Instituto de Biolo- Tehuana Rodriguez Smalley, 1969, are
gia, Universidad Nacional Autonoma de classified in three different tribes (Hypolo-
Mexico (IBUNAM EM-358), were com- bocerini, Potamocarcinini, and Pseudo-
pared with Tehuana lamothei, new species, thelphusini). This high diversity is, in part,
described in this study. It was judged that a reflection of the large number of rivers
the specimens ofP. guerreroensis shouldbe and the abrupt geography of this region.
placed in the genus Tehuana Rodriguez & Pseudothelphusa nayaritae, new species,
Smalley, 1969. Twokeycharactersseparate from the Mexican State ofNayarit, repre-
Tehuana from Pseudothelphusa de Saus- sentsamodifiedformwithinthegenusbased
sure, 1857: theformofthemarginalprocess onitsgonopodmorphology,sinceithaslost
ofthe gonopod, which is rounded and par- thecharacteristicmarginalprocess. Theab-
tially fused to the mesial process in the for- sence ofthe marginal process is a character
mer, and absent or dentiform and com- shared by five other species ofPseudothel-
pletely fused to the mesial process in the phusa found in the western portion ofthe
latter; and the presence in Tehuana, and distributionofthegenus. Thepresumedde-
absenceinPseudothelphusa, ofadefinedsu- velopment of the marginal process (Rod-
perior frontal border ofthe carapace. riguez & Smalley, 1969) shows a sequence
Tehuana lamothei, new species, is de- inwhichthisprocess, startingfromacaudal
scribed from the mountains of northern position (e.g., Potamocarcinus), first reach-
m
Chiapasabove 1000 ofaltitude.Thepres- es the apex of the gonopod (e.g., Spiro-
ent work adds a sixth genus {Tehuana) to thelphusa Pretzmann, 1965), and then be-
the pseudothelphusid crab fauna of Chia- comes recurved over the mesial crest as a
pas. The six genera, Raddaus Pretzmann, conspicuous lobe (e.g., Tehuana and Pseu-
1965; Potamocarcinus Milne Edwards, dothelphusa). All the specimens discussed
1853; Typhlopseudothelphusa Rioja, 1952; here are deposited in the Crustacean Col-
730 PROCEEDINGSOFTHEBIOLOGICALSOCIETYOFWASHINGTON
lection. Institute de Biologia, Universidad Description.—Carapace slightly convex,
Nacional Autonoma de Mexico (IBUN- surface smooth. Superior frontal border
AM). Thegonopodterminologyusedisthat marked by irregular blunt tubercles. Front
proposedby Smalley (1964) and Smalley & smooth, dividedbymediangroove, slightly
Adkison (1984). Carapace width and cara- bilobed in dorsal view (Fig. 4a). Inferior
pace length are abbreviated as cw and cl; frontalborderprominent,composedofblunt
catalog numbers are precededby the letters tubercles, continuous with superior border
EM which denote an access code. oforbits. Median groove narrow and deep,
dividing superior frontal border and front.
Tehuana Rodriguez & Smalley, 1969 Postfrontal lobes elevated, limited anteri-
orly by distinct groove. Cervical grooves
Remarks.—T\\Q genus Tehuana was cre-
arched, deep, wide, not reaching anterolat-
ated to separate a subgroup of species of
eral margin. Gastric and branchial regions
Pseudothelphusawithgonopodsthatexhibit
elevated. Branchial region divided by shal-
a distinctly rounded marginal process only
low depression. Anterolateral margin con-
partially fused to the mesial process and a
tinuous, formed by blunt, irregular denti-
well marked superior frontal border ofthe
cles.Ischiumofthirdmaxillipedtrapezoidal,
carapace. The species are distributed west
distal part wider than proximal part (Fig.
ofthe Isthmus ofTehuantepec (Rodriguez
& Smalley 1969). The five species of Te- Id). Merus ofthird maxilliped broad, with
externalmarginrounded,becomingstraight
huana (T. lamellifrons Rathbun, 1893; T.
distally; innermargin straight, with portion
complanata'RzXhhun, 1905; T. veracruzana
Rodriguez & Smalley, 1969; T. poglayen- at base ofcarpus slightly arched. Ratio ex-
opod/ischium of third maxilliped 0.71.
orum Pretzmann, 1980; and T. diabolis
Rightchelamissing. Leftchela slender, sur-
Pretzmann, 1980) exhibit a progressive in-
facesmooth, withdistinctlargeroundedtu-
crease in size of the mesial process of the
bercle at base offixed finger (Figs, le, 4b).
gonopod on a westward direction from Los
Fingers not gaping.
Tuxtlas region, in the State ofVeracruz. Gonopod curved in lateral view, straight
in cephalic and caudal views (Fig. lb, c).
Tehuana guerreroensis (Rathbun, 1933), Apexwithlateral processoval-shaped, with
new combination sharptriangulartoothorientedcaudally(Fig.
Figs. 1, 4a-b la). In lateral view, marginal and mesial
processes oriented proximally. Mesial pro-
Pseudothelphusa guerreroensis Rathbun,
cessreniform. In cephalicview, apexcavity
1933:360.-Pretzmann, 1965:10.-Smal-
exposed, terminal pore setae visible; mar-
ley, 1970:105.
ginal and mesial processes curved mesially.
Pseudothelphusa {Pseudothelphusa) guerre-
& In caudal view, lateral and mesial crests of
roensis Rodriguez Smalley, 1969:79,
apex of same height, marginal and mesial
fig. 11, pi. 7.-Pretzmann, 1971: 22.-
processescompletely separated, lateral pro-
Pretzmann, 1972:104, figs. 640-642.
cess with large triangular tooth in central
Pseudothelphusa guerreroensis Rodriguez,
section.
1982:135, fig. 87. Remarks.—The holotype of this species
—
Material examined. \ male, cw 38.0 is a female deposited in the Berlin Zoology
mm, cl 24.5 mm; Copanatoyac, Guerrero Museum. Thetypelocalitywasreporteder-
(17°27'N, 98°35'W), 26 Oct 1963, coll. M. roneously in the original description by
Rosas;IBUNAMEM-358. 1 female,cw55.3 Rathbun (1933) to be "Malinaltepec, south
mm, cl 35.0 mm; same locality, date, and of Teopa, Guerrero." The correct type lo-
collector as holotype; IBUNAM EM-358a. cality is "Malinaltepec, south of Tlapa,
VOLUME 107, NUMBER4 731
Fig. 1. Tehuanaguerreroensis,newcombination,a-cleftgonopod:a,lateralview;b,cephalicview;c,caudal
view;d, thirdmaxilliped; e, leftchela. Scalebars: a-d = 1 mm, e = 5 mm.
732 PROCEEDINGSOFTHEBIOLOGICALSOCIETYOFWASHINGTON
Guerrero," and cannot be located precisely dorsal view, deep and wide forming
since "Malinaltepec" isthenameofa small V-shaped notch in front. Postfrontal lobes
mountain range, not ofa town. Rodriguez limited anteriorly by shallow depressions.
& Smalley (1969) described the first male Cardiacregion discernible. Cervicalgrooves
ofthe species from "Copanatoyac, 40 km deep, strongly curved, reaching anterolat-
southwest from the type locality," and also eral marginproducingsmallnotch. Antero-
wronglyreportedthetypelocalityas "Mali- lateral margin with 21-23 small denticles
naltepecsouthofTeapa, Guerrero."Inspite between cervical groove and epibranchial
ofthefactthatthemaledescribedbyRodri- region. Merus ofthird maxilliped with dis-
guez & Smalley (1969), and redescribed in tolateral margin rounded, distal and inner
this paper, cannot be a type specimen, its margins straight (Fig. 2e). Ratio exopod/
description has become the only reference ischium of third maxilliped 0.75. Major
to identify the species. We propose the as- chelaright,innersurfaceglobose,fingersnot
signment ofPseudothelphusa guerreroensis gaping, andcurvedinwardsdistally(Fig. 2f).
tothegenus Tehuana, basedonthepresence Propodus offifth walking leg with distinct
ofa distinct superior frontal border ofthe ridge bearing spines on ventral margin.
carapaceandonthepartiallyfusedmarginal Gonopod curved in cephalic, lateral, and
and mesial processes in the male gonopod. caudalviews,straightincephalicview(Figs.
2a-d). Apex bearing three distinct lobes or
Tehuana lamothei, new species processes. In cephalic view, lateral process
with superior margin describing a semicir-
Figs. 2, 4c
cle, with sharp triangular tooth oriented
Holotype.—Male, cw 27.3 mm, cl 18.2 caudally, and small rounded tooth on ce-
mm; Arroyo La Piedra, 1 km from Ixta- phalic margin. In lateral view, lateral pro-
comitan, Chiapas(17°25'N, 93°05'W),4Apr cess orientedcaudally, marginal and mesial
1986, colls. J. C. Nates, A. Cantii, D. Valle, processes oriented anteriorly at 90° angle
and E. Lira; IBUNAM EM-5604. with respect to longitudinal axis of gono-
—
Materialexamined. 2 males designated pod. Mesial process broadly rounded, par-
as paratypes, cw 33.7, 32.0 mm, cl 21.5, tiallyfusedtomarginalprocess. Smallblunt
20.8 mm; Tapilula, Chiapas (17°15'N, projection on mesial surface closeto mesial
93°01'W), 20 Apr 1981, coll. R. Lamothe, crest, visible in cephalic and caudal views.
IBUNAMEM-8812. 4males, cw22.9, 22.5, Lateral crest ofapex cavityrounded, higher
21.0, 17.3 mm, cl 15.4, 15.0, 14.0, 11.9 than mesial crest. Field of terminal pore
mm; 1 female, cw 34.8 mm, cl 22.2 mm; setae elongated on lateral portion ofapical
same locality and collectors as holotype; cavity.
IBUNAMEM-5604a. 2males,cw37.4, 13.7 Etymology.—This species is named after
mm, cl 23.9, 9.2 mm; 1 female, cw 49.7 our colleague Rafael Lamothe, from Insti-
mm, cl 31.6 mm; same locality and collec- tuto de Biologia at UNAM.
tors as paratypes; IBUNAM EM-8812a. Remarks.—Tehuana lamothei exhibits
Description.-Dorsal surface ofcarapace the keycharactersthatdistinguish Tehuana
slightly convex, smooth, covered with fine from Pseudothelphusa, namely: the con-
punctations.Superiorfrontalborderstraight, spicuoussuperiorborderofthecarapaceand
prominent, formed by small tubercles, di- thegonopod's broadly rounded mesial pro-
vided by deep median notch, disappearing cess, partially fused to the also rounded
laterally behind orbit. In frontal view, in- marginal process. Relative to the other spe-
ferior frontal border continuous, sinuous, cies ofthe genus, the gonopod morphology
thinnerthan superiorone (Fig. 4c). Median places T. lamothei at one end ofthe range
groovenarrowbetweenpostfrontallobes; in ofvariation: it possesses the most reduced
VOLUME NUMBER
107, 4 733
Fig. 2. Tehuana lamothei, new species, a-dleftgonopod: a, lateralview; b, laterocephalicview; c, cephalic
view; d, caudal view; e, thirdmaxilliped; f, rightchela. Scalebars: a-e = 1 mm, f= 5 mm.
734 PROCEEDINGSOFTHEBIOLOGICALSOCIETYOFWASHINGTON
Fig. 3. Pseudothelphusanayaritae, newspecies,a-cleftgonopod: a, mesialview;b,caudalview; c,cephalic
view; d, thirdmaxilliped; e, rightchela. Scale bars: a-d = 1 mm, e = 5 mm.
VOLUME 107, NUMBER4 735
mesial process, that forms a 90° angle with
respect to the longitudinal axis (i.e., orient-
ed anteriorly); and its lateral process is the
largest within the genus. In the other five
species ofTehuana, the mesial process pro-
gressivelyincreasesinsize, isorientedprox-
imally,andthelateralprocessbecomesvery
reduced. This sequence ofgradual morpho-
logicalchange,whichhasbeendescribedfor
otherpseudothelphusidcrabs(Alvarez 1989;
Alvarez(feVillalobos 1991; Rodriguez 1982,
1987), also coincides in species ofTehuana
with their geographical distribution. Te-
huanalamothei, atoneendofthespectrum,
marksthe southeastern limit oftherangeof
thegenus; T.poglayenorumand T. diabolis,
with their intermediate morphology, occur
in the central portion ofthe range; and T.
veracruzana and T. complanata, occurring
to the west, have the most enlarged mesial
process.
Pseudothelphusa de Saussure, 1857
Remarks.—ThegenusPseudothelphusais
distributed in Mexico from the 18°N par-
allel northwards, from the GulfofMexico,
in Los Tuxtlas, Veracruz, across central
Mexico to the Pacific slope. Pseudothelphu-
sa is distinguished from the closely related
Tehuana based on the marginal process of
the gonopod which is completely fused to
the mesial process, and in many species it
appears as a sharp tooth (e.g., P. parabel-
liana, Alvarez, 1989).Themarginalprocess
canbe reducedto a series ofsmall denticles
(e.g., P. jouyi, Rathbun, 1893) or be com-
&
pletely absent (e.g., P. galloi, Alvarez Vi-
Ualobos, 1990). The superiorfrontalborder
ofthe carapace is absentin mostofthe spe-
cies oi^Pseudothelphusa.
Pseudothelphusa nayaritae, new species
Figs. 3, 4d
Holotype.—Male, cw 40.3 mm, cl 23.1 Fig. 4. Tehuana guerrewensis, new combination:
mm; ArroyoElGuayabito, Mecatan, Naya- a, frontofcarapace; b, right chela(cw 38.0 mm). Te-
huanalamothei,newspecies:c,frontofmaleholotype
rit (21°30'N, 105°10'W), 5 Apr 1984, coll. (cw27.3mm).Pseudothelphusanayaritae,newspecies:
R. Lamothe; IBUNAM EM-8820. d, frontofmaleholotype(cw40.3 mm).
736 PROCEEDINGSOFTHEBIOLOGICALSOCIETY OFWASHINGTON
—
Material examined. 1 female, cw 42.6 assigned to the genus Pseudothelphusa with
mm, cl 25.4 mm; same locality, date, and cautiondueto itsdistribution andgonopod
collectorasholotype;IBUNAMEM-8820a. morphology. Pseudothelphusa nayaritae
Description.—Y>or%d\ surface ofcarapace shares with P. galloi, P. jouyi, P. lopho-
&
convex, smooth, covered with small papil- phallus Rodriguez Smalley, 1969, P. re-
lae. Superior frontal border absent; front chingeri Pretzmann, 1965, and P. sonorae
limitedbyafoldingofthecarapace. Inferior Rodriguez & Smalley, 1969, all distributed
frontal border smooth, straight in frontal in western Mexico, the complete reduction
view; slightlybiconvex in dorsal view, con- ofthemarginalprocessofthegonopod. The
tinuous with orbits (Fig. 4d). Region be- vestiges ofthe marginal process are appar-
tween front and postfrontal lobes sloping ent only in P.jouyi, P. lophophallus, and P.
markedly towards front. Postfrontal lobes nayaritae, in the form ofa series of small
discernible. Mediangroove slightlymarked teeth located on the superiorcephalic angle
betweenpostfrontallobes. Cervicalgrooves ofthe mesial process ofthe gonopod. The
deep, straight anteriorly, curved towards lateralprocessofthegonopodinP. nayarit-
gastric region posteriorly, not reaching an- ae is reminiscent ofthat ofthe P. dilatata
terolateralmargin. Cardiacregionindicated Rathbun, 1898, species complex in central
by conspicuousdepressions. Posteriormar- Mexico (Rodriguez 1982). Pseudothelphusa
&
ginofcarapacemarkedlybiconvexindorsal nayaritae, P.peyotensis(Rodriguez Smal-
view. Anterolateral margins smooth, de- ley 1969) and P. leiophrys (Rodriguez &
void ofdenticles. Ratio ofexopod/ischium Smalley 1969), are all found in the State of
ofthird maxilliped 0.58. Major chela right, Nayarit. Pseudothelphusa leiophrys was
surface ofpalm smooth, fingers gaping and originally described from the State of Co-
curving inwards distally (Fig. 3e). lima (Rodriguez & Smalley 1969), and was
Gonopod thick, strong. In mesial view recently collected in Nayarit, from El Du-
(Fig. 3a), mesial processreniform, recurved razno, 2 km north from Los Sabinos
proximally; marginal process reduced to 2 (IBUNAM EM-12294).
small triangular teeth situated on superior
cephalicangleofmesialprocess. Incephalic Acknowledgments
view(Fig. 3b),gonopoddecreasinginthick- We would like to thank Dr. Rafael La-
ness distally; apex ofgonopod with broad
mothe for donating most ofthe specimens
lateral process, rounded superior margin,
includedinthisstudyandA. Cantu, E. Lira,
laterally bearing 2 sharp triangular projec-
tions, forming wide U-shaped notch. In D. Valle, and J. C. Nates, for their help in
the field.
caudal view (Fig. 3c), sperm channel con-
stricted at % ofits length, curved mesially;
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