Gila brevicauda, r. sp. (Osteichthyes, Cypriniformes), A New Fish From The Sierra Madre Occidental of M6xico

Srsvnq M. Nonrus, Janno M. F$cHE& AND W. L. Mttlcxt;rv

Gila brevicauda n. sp. is named from Rio Candamefra, a headwater tributary in the Rio Mayo basin, Chihuahua, M€xico. It ?, storrt-bodied with well-developed basal radii on the scales, relatively numerous lateral-line scales, and L,4-4,1 pharyngeal dentition. It most resembles

G. pulchra of the Rfo Conchos drainage to the east and a form similar to and perhaps conspecific with C. gdehra from the immediately adjacent rios Papig6chic and Fuerte basins (both also in Chihuahua), The new species differs in having an exceptionally abbreviated caudal fin and finer scales. Biogeography and conservation status of G. brevicauda and the transdivide region it occupies are reviewed.

THE cyprinid genus Gila Baird and Girard is widely distributed in western USA and northern M6xico, where it inhabits a variety of habitats, mostly in streams and commonly in arid or semi-arid regions. As with other elements of the western

American fish fauna (e.9., other cyprinid genefa, Salmonidae, Catostomidae), complex geologic, climatic, and hydrographic events have molded a perplexing array of species, morphs, and distributions. Because of their occurrence in arid lands, many species have come into conflict with human interests in this fast-developing region.

Some species or subspecies face acute conservation problems, while others (included taxa as yet unnamed) have already been rendered extinct by human activities.

Derivation of a stable taxonomy for subgroups and species within the genus Gila has proven difficult (Rinne, L976; Smith et al., 1979; Minckley and DeMarais, 2000). Most workers have employed external morphomeristic characters to delineate subgenera and species groups. Uyeno (1961) added osteology, but his work was never published in the open literature and was neither carried forth nor updated.

Only recently have molecular studies contributed to systematic understanding of some taxa (DeMarais, L992; Simons and Mayden, 1998, L999), although a lack of parallel data sets of other kinds limits their usefulness. Whatever the case, species have been variously arranged into taxonomic categories (e.g., Miller, L945; Barbour and Miller, 1978) that have not been particularly stable, with some {e.g., Siphatales

Cope, Snyderichthys Miller) alternatively subsumed within or removed from Gila.

Phylogenetic relations and taxonomic identities of species of Gila, particularly in northern M6xico, are even more poorly understood (see biogeographic reviews by

Smith and Miller, 1986, and Minckley c! al., 1985). Scattered across this vast area there exists or once existed a number of incompletely evaluated populations, including perhaps 10 known or thought to represent unnamed species. Among these is a distinctive headwater form from the Rfo Mayo basin, deep within the Sierra Madre

Occidental of western Chihuahua. We offer its description.

Measurements and counts follow methods Hubbs and Lagler (1958), standard length (SL) is used throughout, and institutional abbreviations follow Leviton et al.

(1985). Dial calipers were used for measurement to the nearest 0.1 mm. Mean values are tl.O standard deviation (s.d.). Principal component analyses were performed on log-transformed raw data (Bookstein et al., 1985). Some meristic data and other observations reported here were collected by Robert R. Miller (RRM; in part attributed below to University of Michigan field number M79-6) or Teruya Uyeno {then at

UMMZ), extracted from original files made available by RRM (see Acknowledgments).

Gila bgeylgaU:da Norris and Fischer, n. sp.

Shorttail chub, carpita cola corta Figuresl-5,Tables1-3

Gila oulchra (in part)-Hendrickson et al. (198I:72; misidentification).

Gila sp. (in part)-Minckley et al. (1986: 590; distribution, upper Rio Mayo).

Holot)'pe: UMMZ XXXXXX (ex-UMMZ 2L23lL), 93.9 mm female, M6xico, Chihuahua,

Rio Candamefra, 1 - 2 km above Cascada de Basaseichic. collected 16 - 17 November

1975 by L. T. Findley, C.L. Constant, and C. H. Lowe, Jr.

Parat)'pes (all Chihuahua, M6xico): UMMZ 212311 (ex-UAZ 75-102),39 specimens (71

- 129 mm SL), same data as holotype. UMMZ 208179,86 specimens (9.0 - 104 mm),

Rio Candamefla, 1.5 km below Highway 23 at turnoff to San Juanito, about 120 km W

of La Junta, 28" 15'W 108o 08'N, 2100 m, collected 9 May 1979 by R. R. Miller, B.

Chernoff, M. Hatch, and T. Uyeno (field no. M 79-6). UANL XXXXX, 8 specimens (51 -

93.9 mm) (ex-UMMZ 208179). UNAM XXXX, 8 specimens (49.1 - 102.3 mm) (ex-UMMZ

248179t. UAZ75-103, 30 specimens (XX - XX mm), Rio Candamefla downstream of

Cascada de Basase6chic, collected 17 November 1975 by D. W. Owens. ASU 9936, XX

specimens (XX - XX mm), tributary to Rio Candamefla, 0.5 km upstream of Cascada de

Basasedchic, collected 5 May 1978 by D. A. Hendrickson and party.

Other material (non-types, not examined) includes ASU 8447, XX specimens (XX -

XX mm, €uroyo along road from Tomochic to Basaseachic 1.0 km upstream from where road crosses il'royo at turnoff to Arroyo San Juanito, known locally as El Durazno just

below confluence of Arroyo La Casita, collected 7 March 1979 by D. A., and S.

Hendrickson, UANL XXXXX, 12 specimens (32.6 - 43.3 mm), Rio Durazno at "Rancho

Nuevo" between La Estrella and Basase6chic, collected L982 by A. Maeda, and UANL uncataloged, uncounted specimens, same locality as UANL XXXXX, collected (undated)

by A. Balderas-Arquieta (S. Contreras-Balderas, pers. comm.). We are unable to pinpoint the locale for the last three collections. There are two zuroyos named "El Durazno" on our available maps, one about 10 km east, and appearing to bypass Cascada de Basase6chic to enter the lower Fjo Mayo system through Rio Conchefio. The other Arroyo Duranzo flows along with an associated

Arroyo Estrella into Rio Candamefla, to enter upstream of Cascada de Basase6.chic. As noted later, we assume the latter is the locality in question.

Diagnosis.--A stout, blunt-headed species of Gila witl:' l,#4,1 pharyngeal teeth, 8 dorsal, and anal rays, and 68.3 +3.4 (60 - 75) scales in the lateral line. It most resembles G. pulchra of the Rio Conchos basin and a similar (perhaps conspecific) form from rfos Yaqui and Fuerte (here referred to Gila, cf. pulehra), but readily separated from these and other Gila by an usually abbreviated caudal fin, usually shorter than the caudal-peduncle length. Gila brevicauda commonly has 8 pelvic-fin rays (although the mode is 9), while G. pulchra and Gila, cf.p1rle}ra nearly always have 9, rarely 8. Gila brevicauda is also more darkly pigmented (with mottled or blotched flanks) than G. pulchra and most Gila, cf. prdehra. Other than caudal-fin length, G. brevicauda differs from G. conspersa of the Aquanaval - Nazas drainage, another species wit}n 44 pharyngeal teeth in the major row, in its strong basal radii and a modal count of 9 pelvic rays.

Description.--Meristic and morphometric data for Gila brevicauda are in Tables 1 - 2.

It is thick-bodied, stout, and rounded, with a deep caudal peduncle and blunt snout

(Figs. L - 2). The maxillae and mandible are subequal in length, and the jaws are terminal to sometimes overhung by the upper lip and snout. The caudal fin is unusually short for Gila, usually less than caudal-peduncle length (Fig. 3). It is more strongly forked and relatively longer in small young than in large adults, where becoming only weakly forked with rounded lobes. Its marked shofiness is a consistent feature of all specimens, not ern artifact of preservation, pre- or post-mortem damage,

or disease. The dorsal, anal, and pelvic fins are triangular with rounded tips, and the pectorals are fan-shaped.

Gila brevicauda has small body scales, averaging 68.3 +3.4 (60 - 75) in the lateral

line, 14.3 +0.9 (L2 - 16) and 8.1 +0.8 (7 - 1o), respectively, above and below the

lateral line, and 32.8 +1.4 (30 - 35) around the caudal peduncle. The flank scales

have well-developed basal radii. There are 8 dorsal and anal rays, 16 pectoral rays

(one specimen of 21 with 15), and an average of 8.6 +0.5 (8 - 9) pelvic rays (Table 1).

As common in Gila, the pectoral and to a lesser extent the pelvic fins are more

expansive in breeding males (Fig. 2).

The few mature males (caught in May) have fine breeding tubercles scattered

across dorsal and dorso-lateral surfaces of the head, opercula, and flanks (including

both dorsal and ventral surfaces of the caudal peduncle); tubercles are also arranged

along anterior margins of the paired fins and radials of unpaired fins (Fig. z).

The gut loops in a single S-shape from the esophagus to the posterior wall of the

body cavity, then forward to the front, and back to the vent. The anterior third is

inflated into an ill-defined stomach, positioned ventrally. The peritoneum is silvery,

heavily overlain with dark melanophores. The vent is positioned just anterior to the

anal-fin origin and is not obviously dimorphic between sexes.

Principal component analyses demonstrate differences in form between Gila brevicauda and G. pulchra and Gila, cf. pulehra. Figure 4 is a plot of factor scores from data excluding the sexual dimorphic pectoral- and pelvic-fin lengths. Given unequal numbers of mature or breeding males zrmong available specimens of different taxa, inclusion of these traits tended to bias the presentation. Table 3 provides factor loadings demonstrating the relative importance for all characters analyzed. When dimorphic features are excluded, caudal-fin length and to a lesser degree eye diameter and caudal-peduncle depth are the main characters driving separation of G. brevicauda from other t.rxa. Note also the lack of substantial separation between G. pldeera and Gila, cf. pulchra .

The new species shows rather drab pigmentation in alcohol, typical of many Gila.

The dorsum and most of the flanks are dark brown, with the later sometimes mottled in mature males and large females. Most specimens larger than about 40 mm are strongly bicolored, with a light tan venter. A dark band passes along the flanks just above the lateral line, losing definition toward the end of the caudal peduncle.

Radials of the dorsal and caudal fins are dusky. Dorsal and lateral surfaces of the head are pigmented similar to the flanks, and its ventral surface matches the venter except for the lower lip, which is darkened. Dark speckles overlie silvery pigment on the ventral two-thirds of the opercula and cheeks ventral to the eye. Juveniles up to

30 mm have their flanks largely unmarked except for a well-developed lateral band, darker and more sharply defined posteriorly. By 35 - 40 mm, the flanks begin to acquire the dark pigmentation described above. A dark, rectangular spot, clearly separated from the lateral band, is at the base of the caudal fin. This spot broadens with age (size) into an ill-defined triangular blotch, only faintly visible by 5O - 50 mm, and usually not discernible in large specimens (maximum SL 129 mm).

Live individuals have a dark-olive ground color (based on color photograph,of a freshly preserved specimen from UMMZ 2O8L79; M79-6). Flank pigments may be more sharply defined in living animals, which along the lateral line may also show a broad, light band the same shade as the venter. This gives the flank a double-banded appearance scarcely apparent in preserved specimens. The paired fins and anal fin are typically unpigmented, although large individuals may show a dark leading edge on the pectorals and scattered melanophores on anal-fin radials. Sexual dichromatism, e.g., red or oftrnge seasonally colnmon in breeding males of Gila ditaenia Miller and a number of other Gila, have not been seen in the new species.

Comparisons.--All but a few Mexican Gila (e.g., DeMarais, 1992; DeMarais and Minckley 1992,1993) are poorly studied, so specific comparisons are tentative at best. Eastward, of the series of G. pulehra and Gila, cf. puletrra surveyed, e. brevicauda most resembles the latter from Rfo Tom6chic (Rio Yaqui drainage), which also is most geographically adjacent. Some scale counts are closer (Table 1), and available specimens from Rio Tom6chic show dusky, sometimes mottled flank pigmentation, similar to G. brevicauda and less like the flat-grey flanks of fish from rio Conchos, Papig6chic, and Fuerte. In addition to G. pglehra and Gila, cf. pulehra on the east, the endorheic Lago de Guzmdn basin (chihuahua) is occupied by G. nigrescens (Girard), larger in size than G. brevicauda (exceeding SL 180 mm), more elongate in body shape and with 2,5-4,2 teeth. In contrast, G. conspersa Garman, distributed south- and eastward in the Nazas - Aguanaval basin (Durango, Coahuila,

Chihuahua), has weakly developed or no basal radii, most commonly 4-4 pharyngeal teeth (rarely 5) on the inner rows with 2 teeth in one or both outer rows, and again is larger (exceeding 165 mm) and more elongate and fusiform in body shape.

RRM (pers. comm.) has long considered the stubby, thick-bodied Gila, cf. pulehra in upper tributaries of the Rio Yaqui (rios Tom6chic and Papig6chic) and upper Rfo

Fuerte (Rio Verde) basins distinct from Rio Conchos populations (see also Minckley et al., 1986). These were not the thrust of the present study, and while we can clearly separate Gila brevicauda, we find fewer, weaker differences between the Pacific-slope populations and G. pulchra from Rio Conchos. Scales of Pacific-slope forms are smaller than in those from Rio Conchos (Table 1), and some populations are more darkly pigmented. Further, the Pacific-slope or Rio Conchos forms show little morphologic differentiation (e.9., Table 2,Fig. 1).

Mexican relatives of Gila brevicauda on the west are G. ditaenia, G. eremica

DeMarais, G. minacae Meek, G. ptltllurca (Girard), and an undescribed form that co- occurs with G. ditaenia in the (io Concepci6n basin, Sonora (DeMarais and Minckley,

1992). A dark basicaudal spot, typical of adult G. ditaenia, G. eremica, G. purpurea, and the unnamed species is poorly developed in G. brevicauda longer than 50-60 mm.

An apparent absence of bright nuptial colors is shared by G. brevicauda and G. plrrygrea; all the others become reddened when in reproductive condition. All but G. minacae have strong basal radii, as in G. brevicauda, but differ in their 2,5-4,2 pharyngeal dentition.

Some of these (Gila ditaenia, G. puryurea) were placed in the subgenus

Temeculina Cockerell by Miller (1945) and Barbour and Miller (1978), characterized in part by a plate{ike dermosphenotic, strong basal radii, and 2,5-4,2 pharyngeal dentition. DeMarais (1991) later added G. eremica. Our re-evaluation of Gila and its relatives is not far enough along to discuss the status of Temeculina, but whatever the case, G. brevicauda (G. oulchra, Gila, cf.pulehra), with tubular dermosphenotics and

S4 pharyngeal teeth in the major row, fall outside present limits of that subgenus.

Minckley et al. (1986) erred in referring them to Temeculina.

Distribution and Habitat.-- Assuming the questionable locality(ies) discussed above is in the Rio Candamefla drainage, Gila brevicauda is known only from that system, a headwater of the Rio Mayo Basin in the vicinity of the 246-m Cascada de BasaseS.chic

(Fig. 5). A single, small collection is available from immediately below the falls, with the remainder from the bedrock-controlled streams and tributaries above. Habitat at the type locality had clear water ("not easily muddied;" M79-6), with hard substrate,

90/o bedrock, boulders, and coarse gravel, and the remainder coarse sand and silt.

Long, deep pools were separated by high-gradient reaches with riffles and low water falls. The only aquatic vegetation was green algae in quiet waters and biogenic films on rocks. Adjacent terrain was comprised of steep cliffs and canyons with shallow soils vegetated with pine-oak-juniper forest (M79-6 and WLM, pers. observ.).

Biologl,--Essentially nothing is known of the biology of Gila brevicauda. RRM (M79-6) reported both juveniles and adults in pools. Timing or other details of reproduction are unknown, although a 9.0-mm postlarva was collected on 9 May 1979. Tuberculate males are as small as 75 mm. It has no obvious trophic specializations. Three of 4 guts examined were empry, the fifth contained aquatic insect parts (two different odonate nymphs, a belostomatid [?] hemipteran thorax, corixid hemipteran head, two different dipteran larvae, and unidentified bits of insect exoskeleton). The adaptive significance (if any) of the shortened caudal fin is unknown.

Biogeography.--Gila brevicauda inhabits a Rfo Mayo headwater draining western slopes near the local crest of the Sierra Madre Occidental. The upper Rio Mayo is essentially surrounded by other Pacific-slope drainages, on the northeast by tributaries of Rio Papig6chic (Rio Yaqui basin), and south by headwaters of Rio Fuerte system (Minckley et a1., 1986). East of the Continental Divide is the Mesa del Norte, drained by Rio Conchos, a tributary of the Rio Grande (Rio Bravo del Norte in M€xico), and several now-endorheic basins formerly tributary to Rio Bravo or draining into dry lake beds of the Bols6n de Mapimi (Smith and Miller, 1986).

The number of fish distributions that cross this part of the Continental Divide indicate some porosity to fish movement since the Sierra Madre Occidental was formed by Early Tertiary volcanism (McDowell and Clabaugh, 1979; Fernrsquia-V.,

1993). Some taxa are clearly of eastern extraction, Campostoma ornatum (Girard),

Codoma ornata Girard, C),prinella formosa (Girard), and Pantosteus plcbcius (Baird and Girard), while others are western derivatives, Gila spp., Catostomus bernardini

Girard, Catostomus cahita Siebert and Minckley, Ictalurus pricei (Rutter), and

Oncorhynchus sp. (Hendrickson et al., 1981; Minckley et al., 1986). Among the Gila,

G. pulchra and its app.rrent relative(s) inhabit eastern slopes of the Sierra Madre

Occidental, the northwestern Mesa del Norte (Rio Conchos), and uppennost reaches of

Pacific Slope drainages (rios Yaqui, Mayo, Fuerte; Miller, 1976, 1978; Hendrickson et 10

a1., 1981: fig. 9).

Perhaps the great antiquity of the Sierra Madre Oeciderrtal highlands has allowed sufficient time for faunal mixing, or interbasin transfers of fishes were promoted by drainage changes resulting from subsequent volcanism, tectonic mobility, and erosion of this precipitous, montane region. Isolation of sub-basins has led further to vzrrying degrees of differentiation. Codoma ornata and P. plcbcigs, for example, appear to represent species complexes (Contreras-B., 1975; Ferris et a1., 1982), while others

(e.g., Campostoma ornatum; Burr, I976) range through a number of drainages and show little apparent differentiation; most have, however, been less-than-thoroughly studied (Smith and Miller, 1985; Minckley et a1., 1986). The known fish fauna of Rio

Candamefla is small, including the eastern Campostoma ornatum and western Codoma ornata, Catostomus cahita or a near relative, and an unnamed Oncorhynchus

(Hendrickson et a1., 1981).

As indicated above, the Rfo Mayo Gila brevicauda is distinct from G. pulebra and

Gila, cf. pulchra. We hypothesize one of these fishes or a progenitor gained access to

Rio Candamefla through an across-basin transfer such as a stream capture or tectonic displacement, diverging once isolated. Alternatively, G. brevicauda could have differentiated after isolation by the forming Cascada de Basaseichic from a G. puleha-like ancestor that later disappeared (or has yet to be discovered) in the Rio

Mayo system. Although taken below the falls, G. brevicauda has apparently been unable to extend its range to adjacent basins (or has been eliminated from them; see, however, above). In this regard, however, only a few samples are available from the remote, rugged, mountainous upper Rio Mayo drainage (Blasius, L996), so additional fishes and populations of G. brevicauda may yet be discovered.

Etvmolog)r.--The name brevicauda, suggested by RRM, is drawn from the Latin, combining brevis (: short) with cauda (: tail). "Short-tail"describes the most obvious 11.

diagnostic feature of this species. It is used as a noun. For common names, we suggest carpita cola corta (Spanish) and shorttail chub (English).

Conservation status.--If as Aldo Leopold (1949) observed, "to keep every cog and wheel isthe first precaution of intelligent tin&ering," then a key coro'llary certainly is knowing just what those cogs and wheels are. Some m€rnagement and conservation efforts for threaterred species and populatiols of Gila have bee'n be harnpered by incomplete understanding of their systematics. Douglas et al. (1989, 1998) and

Minckley and DeMarais (20OO) provided instrtrctive examples regarding Colorado

River forms, and difficulties sometimes encountered simply identifying different species and selecting appropriate unit$ for conservation action. Lack of systematie resolution also hinders the pursuit of broader evolutionary, phylogenetic and biogeographic studies, regionally and worldwide (Minckley et al., 19&6; Greenwood,

1992).

\'Ve have neither recsrt nor specific data on the abundance of Gila brevicauda, and a survey of the region is warranted to determine its status. A large, existing collection (112 specimens) indkates soilre local abundemce as recently as 1979.

According to Arriaga-C. et al. (2000), the Rio Candameria watershed has suffered in the past from over-grazing and deforestation bty tirnber trarvest, and recently by recreational activity. Almost 15,000 kmz of the Rio Mayo watershed is designated by the Mexican Governrnent as an Area de Protecci6n de Flora y Fauna and Parque

Nacional, within which the Cascada de BasaseS.chic area (59 km2) is further set aside as an Area Naturales Protegidas. In the sarne publication, the latter was also identifi'ed as negatively and increasingly impacted by tourism.

Speciftcs are unknown on how these land uses have dfected water quality or fish populations. Rainbow trout, Onchoryznchus mykiss (Walbaum), has, however, also been widely introduced in the region (D. A. Hendrickson, pers. comm.), with yet- t2

unstudied consequences to the local biota. If non-native rainbow are not yet in Rio

Carrdamefra, their er,'entual appe.urtnce may be difficult to prevent. As noted, at least one native trout inhabits regional waters (Hendrickson et al., 1981), and stocking of one or more non-native Oneheirynchus is likely a more serisus threat to indigenous trouts than to other fishes.

ADDITIOT{AI MATERIAL

An asterisk marks specimens included in quantitative analyses (data compiled by the second author); two asterisks indicate series from whkh RRM, T. Uy.eno, or both gathered data we incorporated into reported values (most often extracted were observations on scale radii and pharyrrgeal teeth).

Gilaconspersa--Rio Nazas drainage, Durango: UMMZ 189086, "*UMMZ L677tA,

**UMMZ 167123, *UMMZ 211U84. G. eremica--Rfo Mfttape drainage, UMMZ 716820.

G. nigrescens--Rio Santa Marfa drainage (Lago de Guzman basin), Chihuahua: UMMZ

208232. Rio Casas Grandes drainage(Lago ft Guzrrrilrr basin), Chihuahua: UMMZ

162621. G. pulchra--Rio Conchos drainage (Rio Bravo del Norte basin), Chihuahua:

*FMNH 3507, **FMNH 3528, **UMMZ 16173r, *,**UMMZ 190173, UMMZ 2trl35,

*UMMZ 2I23O4. Gila, ef. pulchra-- Rio Papig6chic drainage (Rio Yaqui basin),

Chihuahua: *UMMZ 1E23El, *UMMZ 1E2387, r'UMMZ 212298, UMMZ 21157E. Rio

Tom6chic (Rio Yaqui basin), Chihuahua: UMMZ 2LL525. Rio Verde (Rio Fuerte basin),

Chihuahua: *,**tlMMZ 1667t1. G. rninacae--Rio Bavispe (Rio Yaqui basin),

Chihuahua: UMMZ 185320. Gila spp.--Rio San Jose (Rio Grande [: Bravo del Norte] basin), Nerv Mexico: *UMMZ 179567. Rio del Praesidia drainage (independerrt,

Pacific-slope basin), Durango: *UMMZ 190935. Rio Tunal drainage {Rio Mezquital [:

Rio San PedroJ basin), Durango: *UMMZ 179551. L3

ACKNOWLEDGMENTS

R. R. Mi[er generously rnade availab]e his extensive unpublished information, opinions, and manuscript copy on the genus Gila, including many data originally gathered by his forrner student, T. Uyeno. This paper benefited imrneasurably frorn access this important body of work, and we acknowledge and thank them both. We also thank G. R. Smith D. N. Nelson (UMMZ) for access to $pecimens in their care and other amenities, and D. A. Hendrickson for pertinent information. S. Contreras-

Balderas and L. Ma. LozaneVillano tboth UANL), and H. Espinosa*6rez (UNAM) provided museum-related assistance. SMN first became aware of this species while processing historic freshwater fish coEections at the University of Arizona, Tucson, funded by the U.S. Bureau of Reclamation and U.S. Fish and Wildlife Service. E. Theriot (UMMZ) took ttre photograph in Figure 2. Much of this work was dorre in space provided by T. Wissing at Miami University, Department of Zoology, assisted in quarrtitative analyses by $. Walker.

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(SMN, JMF) DTPaRTMENT oF Zoolocy, MrAMr UNwpRsny, OxFoRD, OHro 45056, AND (WtM)

DEPARrrranvr or BtorocY, ARtzoNa SrATE UNrv'gnsrry, TEh4pE, AruzoNa g52g5. E-unn (SMN): norri s sm9muoh:Lo . edu;_ ADDRESS CORRESPONDENCE TO SMN. Table 2. Morphometric values (per mille SL) for Gila brevicauda (n: 2I), G.pulebra (15)and Gila, cf. pulehra_(44); n, range are in parentheses when differing from those just given. Measurements are for lengths of structures unless otherwise indicated

Gila brevicauda Gila pulchra Gila, cf. pulchra Holotype Paratypes

SL (mm) 93.9 81.6 t11.8 72.8 t9.5 84.1 t14.3 (62, 6r.3 - L?7.O) (29, 55.8 - 93.2) (54, 54.0-116.8) Preanal 700 705 t 8.9 705 r 6.6 707 xIZ.O (684 - 72r) (694 - 717) (680 - 730) Prepelvic 497 507 t 8.7 519 + 7.8 515 t11.7 (4es - s2s) (s 10 - s42) (488 - s39) Prepectoral ?61 261 t 8.1 284 +IO.7 280 t10.5 (?46 - 78r) (267 - 3O3) (2s8 - 308) Predorsal 551 551 t10.1 581 t 7.8 577 xL4.6 (s39 - s83) (s71 - 501) (s44 - 604) Head 27r 773 t 5.3 293 + 7.4 ?84 + 8.9 (263 - 29O) (278-303) (259-301) Snout 83 81 t 4.1 88 + 4.5 85 + 5.2 ( 74- 90) ( 81- es) ( 76- 98) Eye diameter 59 63 t 5.7 62 + 4.7 61 t 5.0 ( 46- 72) ( s4- 69) ( 48- 76) Interorbital width 33 LZl y9.O I29 + 6.9 125 + 8.5 (10s - 136) (LL7 - r42) (106 - 141) Postorbital to4 101 t'1.6 114 t 5.3 107 t 5.9 ( e3 - 108) (108 - 123) ( e7- 126) Body depth 248 239 111.0 247 +13.5 253 +15.6 (62,2O9 - 263) (29,2t8 - 274) (s4 222 - 287) Table 2. Concluded.

Gila brevicauda Gila pulqh& Gila, cf. pulchra Holotype Paratypes

Caudal peduncle 2r4 227 x9.4 218 + 8.8 216 +9.3 (62,ZIL - 249) (29,20I - 235) {54, L97 - 24L) Caudal-peduncle 118 lZL t 4.6 l2O x9.7 L26 x9.O depth (ro9 - r29) (106 - 133) (108 - 144) Pectoral fin L37 I74 t26.8 2O4 xI8.4 212 t30.5 (137 - 237) (r82 - ?4r) (165 - 269) Pelrdc firr 14L 146 tl0.3 154 t 5.3 157 t13.3 (128, 168) (143 - 164) (134 - 187) Dorsal fin 201 201 t15.7 215 +10.0 2r8 $3.6 (I6L - 23A) (r92 - 22e) (r93 - 24s) Anal fin t7l 175 xlO.Z 188 t 7.9 192 t13.3 (160 " 201) (r7s - r99) (169 - 224) Caudal fin 170 2O7 t22.9 248 tl?.O 238 t19.5 (62, 150 - 249) (29,224 - 277) (50, 192 - 289) Table 3. Factor loadings for principal component scatterplot in Figure 4. Those driving separation are in boldface. Measurements are of structure lengths unless noted otherwise.

Characters PCl PC2 Characters PC 1 PC2

SL (mm) .98 -.16 Interorbital width .91 -09 Preanal fin .98 -.15 Postorbital .93 .13 Prepelvic fin .98 -.10 Body depth .93 -.00

Prepectoral fin .97 .04 eacdaf*Bcdnns.le .88 :r3.4 Predorsal fin .99 -.06 Caudal-peduncle D .90 .05 Head .98 -.03 Dorsal fin .91 .2r Snout .95 -.01 AnaI fin .93 .15 Evs-dralleter .79 :,34 GaudaLia .73 ,hz