Neogene Decapod Crustacea from Southern Chile

Twelve species of Neogene decapod crustaceans are described from late Miocene and early Pliocene deposits in the Valdivia, Osorno-Llanquihue, and Chiloé basins as well as from Mocha Island, offshore from the Temuco Basin, southern Chile. New species of thalassinideans include Ctenocheles notialis and Axianassa? chilensis. Axianassa Schmitt, 1924, has not been reported previously in the fossil record. New species of brachyurans include Trichopeltarion frassinetti, Pirulella antipodea, Chaceon quadrata, Geryon manningi, Phenophthalmus mochaensis, and Chasmocarcinus chiloeensis. Pirulella and Phenophthalmus are new genera and Geryon Krøyer, 1837, is noted in the fossil record for the first time. Extant congeners are primarily known from lower latitude regions. Only Chaceon Manning and Holthuis, 1989, is known from the Chilean coast at present. Key woRdS: Brachyura, Chile, Decapoda, Neogene, Thalassinoidea A N N A L S O F C A R N E G I E M U S E U M Vol. 78, nuMbeR 4, PP. 337–366 15 MaRCh 2010 Neogene marine strata occur at numerous localities along the Chilean forearc (Cecioni 1980; Mordojovich 1981; Encinas et al. 2008b) (Fig. 1). First studied by Darwin (1846), these deposits have been correlated with the Navidad Formation (~34°S), considered to be the reference unit for the marine Neogene of Chile (Cecioni 1980; DeVries and Frassinetti 2003). The first studies generally refer to these units as shallow marine deposits (e.g., Etchart 1973; Cecioni 1978). However, more recent sedimentological and micropaleontological studies indicate that these successions were deposited at bathyal depths (~500-2000 m) during a period of major Miocene subsidence that took place along the Chilean forearc (Gómez 2003; Achurra 2004; Le Roux et al. 2004; Finger et al. 2007; Encinas et al. 2008b). These deposits contain an abundant and diverse fauna and flora including bivalves, gastropods, decapod crustaceans, echinoids, brachiopods, bryozoans, ostracodes, foraminifers, vertebrates, leaves, and pollen (e.g., d’Orbigny 1842; Darwin 1846; Philippi 1887; Troncoso and Encinas 2006; Finger et al. 2007). Most of the paleontological studies have been performed on mollusks (e.g., Tavera 1979; Covacevich and Frassinetti 1986; Nielsen 2005). Decapod studies, on the other hand, have been scarce (e.g., Philippi 1887; Tavera 1979) until recently. In 1985, Chirino-Gálvez noted the presence of decapod crustaceans, along with other benthic faunal elements, in a summary of the paleoecology of the area surrounding Valdivia, Chile. Subsequent field work by one of us (RMF) and Chirino-Gálvez yielded extensive collections of fossil decapods from localities extending from Tierra del Fuego to Navidad, west from Santiago. An unpublished M.S. thesis (Chirino-Gálvez 1993) detailed the history of study of fossil decapods in southern South America, summarized the decapod fauna of Chile, and documented the localities from which decapods were known. Subsequent field work by Encinas, Feldmann, and Schweitzer in 2004 in the vicinity of Navidad resulted in the documentation of 12 species of decapods from the Navidad Formation (Feldmann et al. 2005) and three species from Cretaceous and Eocene rocks of the vicinity (Schweitzer et al. 2006a). Those studies documented, for the first time, tenuous connections between the mid-latitude decapod fauna of Chile and Argentina. During the past few years, collections of fossil decapods made by Sven Nielson and one of us (AE) in the area of Isla Chiloé has prompted examination of the fauna surrounding that locality. In the present contribution, we describe fossil decapods collected from Neogene strata that occur in several different localities of southern Chile (Fig. 2). INTRODUCTION 338 annalS oF CaRnegie MuSeuM Vol. 78 Fig. 1.—Geological map showing the extension of the Neogene marine deposits (dark grey) that crop out along the Chilean forearc. Figure modified from Martínez-Pardo (1990). 2010 FeldMan et al.—neogene deCaPod CRuStaCea FRoM SoutheRn Chile 339 DECAPOD SAMPLE LOCALITIES Decapod specimens have been collected in Neogene strata that crop out in six different localities between Valdivia and Isla Guafo (~40oS 43oS) (Fig. 2). The general lithology and known fauna of crustacean-bearing units as well as the collecting localities for each of these areas are described below. 1) Valdivia. Miocene marine strata that crop out in the Valdivia area (Fig. 2A) were first studied by Brüggen (1950) who correlated this succession with the Navidad Formation. Subsequently, Martínez-Pardo and Pino (1979) defined these deposits as the Santo Domingo Formation after their study of the locality by that name. This unit is exposed in several outcrops of limited dimensions that occur in roadcuts and coastal cliffs around Valdivia. The sedimentary succession consists of a basal breccia overlain by dark-gray sandy siltstones and minor sandstone and breccia (Encinas et al. 2008a). The Santo Domingo Formation contains a rich fossil biota that includes bivalves, gastropods, brachiopods, bryozoans, crustaceans, echinoids, fishes, foraminifers, ostracodes, radiolarians, and leaves (Chirino-Gálvez 1985, and references therein). Benthic foraminifers and trace fossils indicate deposition at lower bathyal depths for this unit (Encinas et al. 2008a). Deposition of this succession took place probably during the late Miocene (see Encinas et al. 2008a, and references therein for discussion). Crab specimens from this area were collected at the following localities: (1) seventeen specimens were collected from the Cuesta Santo Domingo, which is located along the road between Valdivia and Paillaco, approximately 14 km southwest of Valdivia (lat. 39°57’S, long. 73°06’W); (2) one specimen was collected at Rincon de la Piedra, about 10 km southwest of Valdivia (lat. 39°55’S, long. 73°07’W); and (3) three specimens were collected in a roadcut north of Corral (lat. 39°53’S, long. 73°26’W) (Fig. 2A). 2) Caleta Parga. Brüggen (1950) cited the presence of Miocene marine strata that he assigned to the Navidad Formation in the locality of Caleta Parga on the Pacific Fig. 2.—Left half: general map of the study area. The insets show the location of the collecting areas described in the text, except Mocha Island which is indicated on Figure 1. Right half: detailed maps of the collecting areas. Decapod collecting localities are highlighted by arrows. Extension of Neogene marine deposits are shown in grey. 340 annalS oF CaRnegie MuSeuM Vol. 78 coast west of Puerto Montt (Fig. 2B). Tavera (1965) also correlated these deposits with the Navidad Formation based on the presence of Turritella ambulacrum Sowerby, 1846. The succession consists of a basal breccia overlain by dark-gray silty sandstone that contains fossils of bivalves, gastropods, decapods, and lower bathyal foraminifers (K. Finger personal communication). Poorly preserved, partially pyritized decapod claws were collected from this area at Punta Ortiga (lat. 41°26’S, long. 74°08’W) (Fig. 2B). 3) Cucao.—Marine strata assigned to the Lacui Formation (Valenzuela 1982) by Quiroz et al. (2004) occur along the west coast of Chiloé Island south of Cucao (Fig. 2C). The succession consists of sandstone and siltstone beds that locally contain abundant fossils of bivalves, gastropods, foraminifers, scaphopods, cirripeds and decapods (Tavera et al. 1985; Finger et al. 2007). Benthic foraminifers indicate deposition at upper-middle bathyal depths for this succession (Finger et al. 2007). Planktic foraminifers restrict the age of these strata to the Zanclean (early Pliocene, zone N19). A large number of decapod specimens were collected from the Lacui Formation at the northern part of Punta Pirulil approximately 10 km south of Cucao (lat. 42°42’S, long. 74°08’W) (Fig. 2C). These fossils were found in concretions contained in grey siltstones that are exposed in the tidal platform during low tide. 4) Pichicolo. Marine strata assigned to the Ayacara Formation by Levi et al. (1966) crop out near Hornopiren, east of Chiloé Island (Fig. 2E). The succession consists of rhythmically interbedded sandstone, siltstone, and breccia containing abundant volcanic material and interpreted as deposited by turbiditic currents (Levi et al. 1966). The Ayacara Formation contains microfossils of foraminifers and silicoflagellates (Levi et al. 1966). In contrast, the only macrofauna reported from this succession is a single coral specimen assigned to the genus Flabellum Gray, 1849, by Solano (1978), and no crustacean fossils have been reported so far. The age of this unit has been debated. Martínez-Pardo (1961) assigned an Eocene-Miocene age to the Ayacara Formation based upon his study of foraminifera and silicoflagellates obtained from the type section at Ayacara. Subsequently, Martínez-Pardo (1965) assigned a middle Miocene age to the succession of Isla el Manzano (Fig. 2E) based on foraminifera. Rojas (2003) obtained a 40Ar/39Ar dating of plagioclase from an ash bed at Isla el Manzano that yielded a similar age of 16.5+0.5 Ma. In contrast, Bourdillón (in Sernageomin 1995) assigned a late Eocene-late Oligocene age to this unit based on planktic foraminifera. Two fragmentary callianassid claw specimens from this study were collected in a succession of sandstone and siltstone in the western shore of the fiordo Pichicolo (lat. 42°01’S, long. 72°36’W) (Fig. 2E). 5) Guafo island. No stratigraphic studies have been performed in the Neogene of Guafo Island with the exception of a very general stratigraphic column published by Tavera et al. (1985). Frassinetti (1997, 2000) cited the presence of sandstone and siltstone beds containing fossils of bivalves, gastropods, brachiopods, echinoderms, and crustaceans in these strata. He correlated the molluscan fauna of this unit with those of the Guamblin succession (45oS) and the Tubul Formation of Arauco (37oS), and based on their similarities suggested a late Pliocene age for the marine succession of Isla Guafo. A single crab specimen was collected in 1983 by Frassinetti and Covacevich during his trip onboard the R/V Hero at the locality of Punta Yañez (lat. 43°37’S, long. 74°36’W) (Fig. 2D). 6) Mocha Island. Tavera and Veil (1958) reported exposures of the Ranquil Formation on the northern coast of Mocha Island (Fig. 1) and collected numerous invertebrate fossils, including decapod crustaceans (Chirino-Gálvez 1993). Based upon the enclosed fauna, the age of the Ranquil Formation was considered to be Miocene in age. Institutional Abbreviations.—BM In, The Natural History Museum, London, United Kingdom; KSU, Department of Geology, Kent State University, Kent, Ohio, U.S.A.; SGO.PI, Museo Nacional de Historia Natural, Sección Paleontología, Santiago, Chile; USNM, United States National Museum, Smithsonian Institution, Washington, D.C., U.S.A. SYSTEMATIC PALEONTOLOGY Infraorder Thalassinidea Latreille, 1831 Superfamily Callianassoidae Dana, 1852 Family Ctenochelidae Manning and Felder, 1991 Ctenocheles Kishinouye, 1926 Type Species.—Ctenocheles balssi Kishinouye, 1926, by monotypy. Included Fossil Species.—Ctenocheles anderseni Collins and Jakobsen, 2003; Ctenocheles chattiensis Polkowsky, 2004; Ctenocheles cookei (Rathbun, 1935), as Ischnodactylus; Ctenocheles cultellus (Rathbun, 1935), as Ischnodactylus; Ctenocheles dentatus (Rathbun, 1935), as Ischnodactylus; Ctenocheles falciformis Collins and Todd in Todd and Collins, 2005; Ctenocheles hokoensis Schweitzer and Feldmann, 2001a; Ctenocheles inaequidens (Pelseneer, 1886), as Ischnodactylus; Ctenocheles madagascariensis Secretan, 1964; Ctenocheles maorianus, Powell 1949; Ctenocheles notialis, new species; Ctenocheles ornatus Beschin, De Angeli, Checchi, and Zarantonello, 2005; Ctenocheles rupeliensis (Beurlen, 1939), as Thaumastocheles; Ctenocheles secretanae Schweitzer and Feldmann, 2002; Ctenocheles sujakui Imiazumi, 1958; Ctenocheles valdellae (Fabiani, 1908), as Ilia (?);Ctenocheles victor Glaessner, 1948. 2010 FeldMan et al.—neogene deCaPod CRuStaCea FRoM SoutheRn Chile 341 Ctenocheles notialis, new species (Fig. 3) Diagnosis.—Major claw with bulbous manus tapering distally into uniformly high, straight fixed finger directed downward at 35° angle from long axis of manus. Description.—Manus of right, major cheliped ovoid, longer than high; transversely inflated, greatest height appears to be at about midlength. Fixed finger long, broad proximally, tapering rapidly to slender, ovate form with acute tip on lower surface. Finger directed downward at about 35° angle from long axis of manus. Denticles vary in length from about 0.5 mm to 1 mm, pectinate, directed slightly proximally; larger teeth separated by one to four shorter teeth. Terminus of finger curved upward into proximally directed tooth. Other elements missing. Measurements.—Holotype: length of manus 8.9 mm; height of manus 7.3 mm; thickness > 4.3 mm; length of fixed finger 11 mm. Paratype 1: length of manus 7.7 mm; height of manus 4.3 mm. Paratype 2: length of manus 8.1 mm; length of fixed finger 12.5 mm. Etymology.—The trivial name is taken from the Latin word notialis meaning southern, in reference to the southern latitude from which the specimen was collected. Types.—The holotype, part and counterpart, SGO.PI. 6554, and three paratypes, SGO.PI. 6555-6557, are deposited in the National Museum of Natural History, Santiago, Chile. Occurrence.—The holotype was collected from the Lacui Formation, early Pliocene, in coastal exposures near Punta Pirulil, south of Cucao, Chiloé Island, Chile at lat. 42°42’S, long. 74°08’W. The paratypes were collected from the Santo Domingo Formation, late Miocene, at Santo Domingo, southwest of CH 207, about 10 km southeast from Valdivia, Chile approximately at lat. 39°53’S, long. 73°10W. This locality is a roadcut near Piedra Blanca. Discussion.—The bulbous form of the manus of the major claw and the downturned, slender, pectinate fixed finger conforms fully to the morphology of extant and extinct members of Ctenocheles. Comparison of the morphology of C. notialis with all other fossil species confirms that the specimen from Chiloé is unique. The diagnostic characters noted above represent a plexus of characters that none of the other species possess. The outline of the manus; the height of the fixed finger; the longitudinal profile of the fixed finger, whether straight or curved; the form of the denticles on the occlusal surface; and form of the proximal part of the fixed finger are characters diagnostic of species within the genus. The morphologically most closely related species seems to be C. maorianus, originally described as living in soft mud at depths of 19-30 fathoms, and subsequently reported from the Pleistocene of New Zealand (Feldmann and Keyes 1992). The hand is bulbous, the fixed finger lies at an angle of about 30° to the long axis of the manus, and the pectinate denticles are directed slightly proximally. The species differs in that the proximal part of the fixed finger does not heighten to the same degree in C. maorianus that it does in C. notialis, and the distal margin of the former species curves more gently and over a greater length of the finger than seen on the latter species. Thus, the specimen from Chiloé represents a new species. The holotype consists of a broken, corroded major cheliped surrounded by fragments of decapods, probably more fragments of Ctenocheles, and fish scales, vertebral centra, other fish parts, and fragments of gastropods. This mass of small fragments forms an ovoid nucleus of a concretion whose long axis is slightly longer than the long axis of the nucleus. Unlike the typical concretions in the Lacui Formation, a mold of a snail with cancellate ornamentation protrudes from one end of the concretion, and the Ctenocheles claw extends just to the opposite end of the nucleus. This accumulation of fragments nested within the concretion appears to be a coprolite or regurgitate. The paratypes from the Santo Domingo Formation occur within the matrix of grey, micaceous, sandy siltstone. The presence of the micaceous particles imparts a platy structure to the matrix. Fig. 3.—Ctenocheles notialis, new species. A, holotype, SGO.PI. 6554; B, paratype, SGO.PI. 6555. Scale bars equal 1 cm. 342 annalS oF CaRnegie MuSeuM Vol. 78 Family Laomediidae Borradaile, 1903 Included Genera.—Axianassa Schmitt, 1924; Jaxea Nardo, 1847; Laomedia de Haan, 1847; Laurentiella LeLoeuff and Intès, 1974 (all have fossil representatives); and Espeleonaushonia Juaerro and Martinez-Iglesias, 1997; Naushonia Kingsley, 1897 (both lacking a fossil record). Diagnosis.—See Ngoc-Ho (1997). Axianassa Schmitt, 1924 Type Species.—Axianassa intermedia Schmitt, 1924, by monotypy. Diagnosis.—See Kensley and Heard (1990). Discussion.—The specimens can be excluded from most shrimp, lobster, and thalassinidean groups based upon the unusual shape of the carpus. It is very short, and does not extend the entire height of the manus, so that it appears to articulate either with only the upper proximal margin of the manus or with the upper proximal margin and a point part-way along the proximal margin. It does not extend to the lower proximal margin of the manus. The distinctive shape of the carpus, being small, short, triangular, and widening distally, is seen in members of the Laomediidae. The Laomediidae is not well represented in the fossil record. The existing diagnoses do not list many features that are usually preserved in fossils, but examination of illustrations of species of Laomedia (in Ngoc-Ho 1997) and Axianassa (in Kensley and Heard 1990), the two most speciose genera in the family, indicate that the carpi are small and widen distally; the meri are ovate; and the mani may be markedly heterochelous. This combination of characters is seen in the specimens described here. The unusual size and shape of the carpus, wherein it is much narrower than both the manus and merus, seems to be characteristic of this family. Of the six genera currently placed within the Laomediidae, the specimens are best placed within Axianassa, based upon the occurrence of the unusual articulation of the carpus and manus seen in some species of Axianassa (illustrations in Kensley and Heard 1990). In addition, members of the Laomediidae, including Axianassa, may have strongly heterochelous first pereiopods as seen in the specimens described here. Thus, a questionable referral to Axianassa, given the incomplete nature of the material, seems best at this time. Axianassa is known from Pacific coastal Panama, coastal Mexico, and the Caribbean in modern oceans (Kensley and Heard 1990). Within the Laomediidae, only four extinct species are known, including Jaxea kuemeli Bachmayer, 1954, from the late Miocene (Tortonian) of Austria (Bachmayer, 1954), J. cf. nocturna Nardo, 1847, from the MiocenePliocene of Spain (Müller 1993), and Laomedia praestacina Karasawa, 1989, and Laurentiella imaizumii Karasawa, 1993, from the early Miocene of Japan. The one extant species of Jaxea, Jaxea nocturna Nardo, 1847, has been reported in Pliocene rocks of Italy (De Angeli and Garassino 2006). Axianassa? chilensis, new species (Fig. 4) Diagnosis.—First pereiopods heterochelous; carpus narrow proximally, widening distally, distal margin articulating with upper proximal margin of manus; inner surface of manus of gracile claw with scabrous rows of tubercles; distal margin thickened; inner surface of fixed finger with flattened platform; robust claw with large denticles on fingers. Description.—First pereiopods heterochelous. First pereiopod with gracile claw with ovate merus; longer than high; inner surface flattened; distal margin nearly straight. Carpus narrow proximally, widening distally; upper margin nearly straight; lower margin sloping toward lower margin; about as high as long when height measured at highest point; distal margin articulating with upper proximal margin of manus, not entire proximal margin of manus. Manus approximately rectangular, upper and lower margins weakly convex; lower margin with row of setal pits, upper margin with row of tubercles; proximal margin weakly concave; distal margin thickened; inner surface Fig. 4.—Axianassa? chilensis, new species. A, paratype, SGO.PI. 6559; B, holotype, SGO.PI. 6558. Scale bar equals 1 cm. 2010 FeldMan et al.—neogene deCaPod CRuStaCea FRoM SoutheRn Chile 343 covered with scabrous ridges of tubercles, tubercles directed distally, ridges oriented parallel to proximal margin. Inner surface of fixed finger with smooth platform on occlusal surface, narrow, sharp teeth on outside edge; inner surface of finger smooth. Robust claw with granular outer surface of merus, tubercles directed distally; lower margin with rim distally, rim extending onto fixed finger; distal margin with broad, thickened rim. Fixed finger with sharp teeth proximally on occlusal surface. Movable finger stout, high, with stout denticles proximally. Measurements.—Measurements taken on specimens of A.? chilensis, holotype: SGO.PI. 6558: manus length including fixed finger (ML1), >20.0 mm; manus height (MH), 7.4 mm; manus length excluding finger (ML2), 7.9 mm; length of movable finger (MFL), >11.5 mm; carpus length (CL), 4.5 mm; carpus height (CH), 4.0 mm. SGO. PI. 6559 gracile chela: ML1, 22.0 mm; MH, 7.0 mm; ML2, 7.3 mm; MFL, 14.5 mm; CL, 5.2 mm; CH, 3.2 mm; merus length, 8.8 mm; merus height, 5.4 mm. SGO.PI. 6559 robust chela: fixed finger length, 10.8 mm; MFL, 11.0 mm. Etymology.—The trivial name is derived from Chile, the country from which the material was collected. Types.—The holotype, SGO-PI. 6558, and two paratypes, SGO-PI. 6559 and 6560, are deposited in the National Museum of Natural History, Santiago, Chile. Occurrence.— The holotype and one paratype, SGO.PI. 6559, were collected from the Lacui Formation, early Pliocene, in coastal exposures near Punta Pirulil, south of Cucao, Chiloé Island, Chile at lat. 42°42’S, long. 74°08’W. One paratype, SGO.PI. 6560, was collected from the Santo Domingo Formation, late Miocene, at Santo Domingo, southwest of CH 207, about 10 km southeast from Valdivia, Chile approximately at lat. 39°53’S, long. 73°10’W. This locality is a roadcut near Piedra Blanca. Discussion.—The specimens are fragmentary, but because they retain portions of the merus and carpus, we refer them to a new species. More complete material, including complete meri and possibly portions of the carapace, could confirm the generic placement in Axianassa. This would mark the most southerly occurrence of the genus in the Americas. Infraorder Brachyura Latreille, 1802 Superfamily Cancroidea Latreille, 1802 Family Atelecyclidae Ortmann 1893 Trichopeltarion A. Milne-Edwards, 1880 Trichopeltarion A. Milne-Edwards, 1880:19. Trachycarcinus Faxon, 1893:156. Type Species.—Trichopeltarion nobile A. Milne-Edwards, 1880. Included Fossil Species.—Trichopeltarion berglundorum Schweitzer and Feldmann, 1999; Trichopeltarion decorus (Rathbun, 1945), as Trachycarcinus; Trichopeltarion frassinetti, new species; Trichopeltarion granulosa Schweitzer and Salva, 2000; Trichopeltarion greggi Dell, 1969; Trichopeltarion huziokai (Imaizumi , 1951), as Trachycarcinus; Trichopeltarion inflatus (Kato, 1996), as Trachycarcinus; Trichopeltarion levis Casadío et al., 2004; Trichopeltarion merrinae Schweitzer and Salva, 2000. Diagnosis.—See Salva and Feldmann (2001). Discussion.—Trichopeltarion is a distinctive genus whose species have complex marginal spines, often with a very large spine at the junction of the anterolateral and posterolateral margins. The genus embraces individuals that are pentagonal in outline and others that are nearly circular, and ornamentation of the carapace varies from granular to coarsely nodose, giving them quite a different appearance. However, Salva and Feldmann (2001) illustrated a range from one morphotype to the other in the growth series of a single species. This observation reinforces the unity of the genus despite the broad range of forms. Extant species of Trichopeltarion typically inhabit outer sublittoral to bathyal water depths (Sakai 1976; Guinot 1989; Salva and Feldmann 2001), which is consistent with the interpretation of the Neogene rocks of the Chilean coast in this area being deposited at bathyal depths. Trichopeltarion levis Casadío et al., 2004 (Fig. 5) Trichopeltarion levis Casadío, De Angeli, Feldmann, Garassino, Hetler, Parras, and Schweitzer, 2004:35. Trichopeltarion levis Casadío et al., 2004 in Feldmann et al., 2005:438. Studied Specimens.—Three specimens, SGO.PI. 65616563, deposited in the National Museum of Natural History, Santiago, Chile, were collected from the Santo Domingo Formation at Santo Domingo, southwest of CH 207, about 10 km southeast from Valdivia, Chile approximately at lat. 39°53’S, long. 73°10’W. Diagnosis.—See Casadío et al. (2004:35). Description of Material.—Carapace ovoid, moderately vaulted transversely and longitudinally; margins spinose; regions tumid and bearing coarse nodes. Front broken, downturned weakly and axially sulcate. Upper orbital margin poorly preserved, slightly elevated, with two (?) supraorbital spines. Anterolateral margin convex, with four long, dorsally granular spines; spines radiate from anterolaterally directed to laterally directed; last spine defines anterolateral corner. Posterolateral margin convex, short, bearing two smaller, blunt, coarsely granular spines. Posterior margin appears to be broken. Carapace regions defined as nodose swellings separated by smooth depressed grooves. Axial regions narrow. Mesogastric region elongate, triangular, with large axial node posteriorly, a smaller node anterior to it, and depressed in anterior half. Mesogastric and urogastric regions not differentiated; transversely ovoid, bearing prominent axial node. Cardiac region with two posterodorsally directed, blunt, granular nodes arrayed transverse to longitudinal axis. Intestinal area not seen. Epigastric and protogastric regions not well separated from one another, broad, elevated, bearing large boss posteriorly and smaller one at midlength; longitudinal 344 annalS oF CaRnegie MuSeuM Vol. 78 axis of regions converge slightly toward front. Hepatic region weakly elevated, with central node. Branchial regions undifferentiated, bearing large, granular node at level of posterolateral corner and smaller node situated posteriad and axiad of large node. Cervical groove a concave forward arc around mesogastric region, curving anterolaterally around posterior margin of hepatic region. Branchiocardiac region not expressed. A single appendage article, interpreted to be the right merus of first pereiopod, three times as long as high; upper surface with at least eight elongate, sharp spines directed upward and distally; outer surface with about 16 blunt nodes arrayed in two longitudinal rows; lower surface appears smooth. Proximal articles of two other appendages on left side of holotype appear to be pereiopods 4 and 5; however, they are too poorly preserved to characterize. Ventral surface of carapace, abdomen, and other appendages not