Axiopsis eximia, a New Thalassinidean Shrimp (Crustacea, , Axiidae) from the Middle Eocene of South Carolina Author(s): Brian Kensley and Austin B. Williams Source: Journal of Paleontology, Vol. 64, No. 5, (Sep., 1990), pp. 798-802 Published by: Paleontological Society Stable URL: http://www.jstor.org/stable/1305715 Accessed: 25/07/2008 10:17

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http://www.jstor.org J. Paleont.,64(5), 1990, pp. 798-802 Copyright? 1990, The PaleontologicalSociety 0022-3360/90/0064-0798503.00

AXIOPSIS EXIMIA, A NEW THALASSINIDEAN SHRIMP (CRUSTACEA, DECAPODA, AXIIDAE) FROM THE MIDDLE EOCENE OF SOUTH CAROLINA BRIAN KENSLEY1 ANDAUSTIN B. WILLIAMS2 'Departmentof InvertebrateZoology and 2National MarineFisheries Service SystematicsLaboratory, National Museum of NaturalHistory, SmithsonianInstitution, Washington, D.C. 20560

ABSTRACTr-Axiopsiseximia, a new species of thalassinideanshrimp, is describedfrom an exposureof the Middle Eocene Lower WarleyHill Formationof South Carolina,U.S.A. Fossil axiids are rare,but this unique specimenis remarkablypreserved as quartz free of envelopingmatrix, having a nearlycomplete though distortedcarapace, proximal parts of most thoracicappendages in situ but with distal articlesmissing, and extendedabdomen with segmentsalmost completeexcept for a few missingappendages. Presence of the bases of pleopods 1 and the elongateeyestalks surpassing the rostralapex, which it shareswith the extantAxiopsis caespitosa group, place it provisionallyin Axiopsis,which generallylacks first pleopods in males.

INTRODUCTION with the specimen contained a single species each of the bivalve molluscs Cardita, Venericardia, and "Corbula," the gastropod FOSSILrecord of the Axiidae (summarized by Glaessner, Turritella, and the scaphopod Dentalium. THE sheds little on the of this 1969) very light understanding The cephalothorax and abdomen of the shrimp are closely diverse about 19 extant Of the six family containing genera. connected as in life, as are the mouthparts and proximal articles fossil one is genera, represented only by coprolites (Palaxius of the cephalic and thoracic appendages. It seems unlikely that Br6nnimann and reticulatus Norton, 1960). Rathbun, the specimen is a molt, but it is likely that the was rapidly from the of is a 1919, Oligocene Panama, represented by single buried, perhaps during a storm, thereby preventing the disar- chela. Placement in the Axius in this case was incomplete genus ticulation usually accompanying decay of the fragile parts. The a matter of the chela obviously convenience, single providing high permeability of the matrix with its quartz content probably no indication of the true The specimen's systematic position. facilitated replacement with silica dioxide. In section, the exo- four Etallonia Pro- remaining genera, Oppel, Magila Miinster, skeletal material is replaced with a fine crystalline white quartz, taxius and Schlueteria are all from the Jurassic Beurlen, Fritsch, while the inner region is replaced with a more translucent aga- or Cretaceous of of these taxa are almost Europe. Specimens tized quartz. and the details of and always laterally compressed, carapace Measurements.-Total length from tip of rostrum to base of needed for and accurate appendages comparison placement telson, 46.0 mm; length of rostrum, 3.0 mm; estimated carapace within the are The taxonomic family rarely preserved. position length including rostrum, 19.0 mm; abdomen, length in mid- of the fossil been established present specimen has, therefore, dorsal line from anterior exposed part of segment one to pos- with extant forms. by comparison terior margin of segment six, 27.0 m, maximum width, 8.0 mm, SYSTEMATIC PALEONTOLOGY length of segment one, 2.4 mm, two, 4.2 mm, three, 5.1 mm (est.), four, 4.7 mm (est.), five, 4.6 mm, six, 6.0 mm. Order DECAPODA 1803 Latreille, Diagnosis. -Rostrum narrowly elongate triangular, dorsally Suborder 1963 Burkenroad, concave, lateral margins bearing six well-developed teeth; gas- Infraorder THALASSINIDEA 1831 Latreille, tric region bearing central elongate oval field of scattered sharp THALASSINOIDEA 1831 Superfamily Latreille, tubercles, median carina at base of rostrum crested with six AXIIDAE 1879 Family Huxley, spines anteriorly; postorbital margin bearing three tiny acute Genus Axiomsis 1903 Borradaile, spines and at its lower limit a larger buttressed antennal spine; EXIMIA n. AXIOPSIS sp. eyestalk exceeding rostrum by half its length; antennular pe- 4 Figures 3, duncle with stout basal article tapering distally and bearing slen- Collection. - Holotype, USNM 219431. One specimen from der distolateral spine; second article subcylindrical, bearing slen- road cut on South Carolina route 261, 1.7 mi south of U.S. der distolateral spine; antennal peduncle with short basal article route 76, about 2 mi north ofWedgefield, Sumter County, South bearing ventral tubercles and spines, stout second article much Carolina (Figure 1). Collected by F. S. MacNeil, U.S. Geological longer and third article more slender, each bearing mesial and Survey Locality No. 25750, August 1950. lateral spines. The locality was revisited by W. Blow (Smithsonian Insti- collapsed posterior to region of cer- tution) almost 30 years later. The small exposure (maximum vicalDescription.--Carapace groove; left branchiostegite collapsed but surface tubercles vertical height about 2 m), cut into a low hill, yielded matrix visible; proximal parts of most cephalothoracic appendages containing molluscs, but no further fossils. present, arranged in normal position of repose but with distal This exposure was determined to be an outlier of the Lower articles missing; abdomen extended, segments almost complete, Warley Hill Marl (Figure 2). Definitions of the Warley Hill Marl proximal articles of two pleopods present, uropods and posterior and description of its type locality were reviewed by Siple (1959). part of telson missing. The Warley Hill Marl is regarded as of middle Eocene age in Rostrum narrowly elongate triangular, dorsally concave, acute western and central South Carolina (Keroher et al., 1966). tip reaching to distal third of second article in antennular pe- Preservation.- The specimen was taken from an iron-stained duncle; thin raised lateral margins with six well-developed teeth, argillaceous, calcareous, medium-to-coarse quartz sandstone distal teeth somewhat eroded, proximal teeth acute, erect; dorsal containing a roughly layered coquina, and is remarkably com- surface moderately troughlike, with transversely rounded con- plete and free of matrix. The small sample of matrix collected cavity gradually broadening to juncture with gastric region; latter 798 KENSLEY AND WILLIAMS-NEW EOCENE SHRIMP 799

0 5 10 15 20 Series Group Formation KMK

Jackson Barnwell

261 15 521 Castle 76-378 E Upper Hayne limestone

Sumter 76-378 Wedgefield

15 0 521

261 a 0 8100 C K M McBean Santee Middle limestone E b

0 FIGUREI1-Location of typelocality of Axiopsiseximia n. sp. in South N Carolina. r WarleyHill marl En with central elongate oval field of scattered sharp tubercles; median carinaat base of rostrum to development rising greatest e Lower Congaree crestedwith six well-developedspines on anteriorgastric region, becoming obsolete in tuberculategastric field; latter flankedby submarginalspineless tract, crescentic row of spine-tippedgran- broadercrescentic concave tract confluent with ules, spineless FIGURE2-Stratigraphic position of Axiopsiseximia n. sp. in Eocene dorsal surface of rostrum, and prominent lateral spiny ridge rocksof SouthCarolina. confluentwith rostralmargin. Each of these tractstrend slightly towardmidline posteriorly,but collapseof carapacebeyond that point prevents description. Postorbital margin confluent with lateral edge of rostrum at level of juncture with lateral gastric tral tip by nearlyone-third length, not includingmissing corneal ridge, with three tiny acute postorbitalspines, largerbuttressed bulb evidently at least one-fourthwider than shaft of stalk. marginal antennal spine at lower limit; anterolateral angle Antennularpeduncle with stout basalarticle tapering abruptly rounded;cervical groove missing, except possibly for obscure in distal fourth of length, exceedinglyslender distolateral spine sector on right side, but lateral surfaceanterior to it granulate; on shoulderof taperingbasal part;second articlesubcylindrical, fragment of posteroventral part of carapace exhibits gently exceedingrostrum by at least half its length,row of three spines curved, entire, slightly raised margin. on mesiodorsal aspect; elements distal to this fragmentaryor Abdomen with smooth terga;terga of segments 3 and 4 im- missing, bases of two flagellavisible. perfectlypreserved; moderate lateralridge definingjuncture of Antennal peduncle with short, triangularlyprismatic basal terga and pleura of segments 1-5, becoming obsolete antero- articlebearing few blunt ventraltubercles and threespines; stout laterally on segment 6; segment 1 pleuron narrow, drawn to second article much longer, bearingslender acute anteromesial ventral point, anterior margin oblique, much longer than pos- spine on inflated mesial margin exceeded by strong anterior terior margin; segment 2 pleuron broadly rounded, flared an- spine on dorsolateralridge, lateralaspect broadlyrounded, row terior edge narrowlyoverlapped by that of segment 1; segment of six or seven tubercles/spineson ventromesial margin;third 3 pleuronnot well preserved,margins appearing essentially equal, segmentmuch more slender,distal marginbearing mesial spine slightly convex, drawn to obtuse ventral tip as are pleura of exceeding rostral tip, spines or tubercles scattered on mesial, segments4 and 5; segment 6 pleuronflared laterally into broad, dorsal, and lateral aspects; elements distal to this fragmentary obliquely horizontal structure separated by deep, narrowly or missing; antennal scale/spine missing. rounded notch from smaller subtriangulo-rectangularpostero- Mouth region partiallyexposed; epistomial plate with trian- lateralcontinuation, both parts forming stop for extended uro- gularly acute apex preceded by margins raised to thin sharp pods. Only lyre-shapedproximal part of telson preserved,me- edges; lateral apices of plate drawn to a spine buttressed by dian tract less elevated than parts to either side, basal part posterolateralmargin; surface of plate uneven, elevated and ornamentedwith rugae,sharp granules, pair of small submedian irregularlyspined anterolaterally. spines; ventral aspect with longitudinallyoblique submarginal Basal remnantsof labrum visible; broken remnantsof man- thin ridge near anterolateralcorner, evidently interlockingwith dibles visible underoverlying maxillipeds; endopod of firstmax- extended uropods. illipeds exposed, smoothly arched, apparently submarginally Appendagesunusually well preservedand exposed;left eyes- setose on cupped mesial aspect, basal curved remnantof endite talk (rightmissing), originating near base of rostrum,with slight present. lateralcurve nearbase, thereafternearly straight, exceeding ros- Second maxilliped with triangular basis; merus elongate, 800 JOURNALOF PALEONTOLOGY,V. 64, NO. 5, 1990

1

L2~

38

FIGURE3-Axiopsis eximia n. sp. 1, dorsal view showing rostrumconfluent with spinose gastric region on cephalothorax;collapsed carapace posterior to cervical groove; proximal parts of cephalothoracicappendages in normal position of repose; extended abdomen with terga of segments 1-6 almost complete, but uropodsand posteriorpart of telson missing;2, left lateralview showingrostrum and spinose gastricregion in profile;collapsed carapaceposterior to cervical groove; proximalparts of eyestalk,antennal peduncle, pereopods 1-4; abdominal segments 1-6 with pleuraalmost complete;part of telson; fragmentof pleopods 3 and 5; 3, enlargementof abdominalsegment 5 with pleopod attached, segment 6 showing notched lateral marginand proximal part of telson ridged ventrallyfor interlockingwith extended uropod, ventrolateral view. Scales: 1, 2 = 5 mm; 3 = 1 mm.

r FIGuRE4-Axiopsis eximia n. sp. 1, dorsalview of rostrum,part of spinose gastricregion, left eyestalk(corneal bulb missing),parts of antennular and antennalpeduncles, and pereopods 1 and 2: 2, 3, mouth field showingepistomial plate; parts of mandibles;basal part of labrum;second maxilliped with curved merus and very short carpus-dactylat right angle to it; third maxillipedwith triquetrousischium bearingmesial row of spines, followed by portion of volute merus;4, pair of broad sternalplates between coxae of pereopods4, precededby sternumand coxae of pereopods 3; 5, part of abdominal segment 6 with notched lateral margin for receptionof extended uropods, and anteriortelson, dorsal view; 6, same in ventral view showing submarginalanterolateral ridge on telson for interlockingwith extended uropods.Scales = 1 mm. KENSLEY AND WILLIAMS-NEW EOCENE SHRIMP 801

r sl

3

r 6 802 JOURNALOF PALEONTOLOGY,V. 64, NO. 5, 1990 curved, slightly twisted; short carpus bent at nearly right angle; the stalk. The narrow rostrum and carapacial spination of the propodus compressed, broadened; dactyl compressed, almost Pacific species, however, easily distinguish it from the present circular. fossil. Until the unsatisfactorily understood composition of Ax- Third maxilliped with polygonal coxa spined on posterior iopsis is resolved, the present specimen must remain in this margin; ischium triquetrous; ventral spine on basis followed by genus. row of five irregularly spaced spines on ventral ridge ofischium, This specimen represents the first occurrence of an axiid whose latter with cluster of small spines near mesioproximal end, comb preservation allows close comparison with extant forms. Its of 13 strong spines on mesial aspect, distalmost pair of spines resemblance to forms such as Axiopsis caespitosa indicates that growing from common base; merus volute, row of six spines on at least one of the extant axiid genera (even if not officially ventrolateral margin stronger distally; elements distal to this designated) had already evolved by the Eocene. missing. Etymology.- The specific name is from the Latin eximius, Proximal articles of pereopods strong and spiny; pereopod 1 choice, exceptional, extraordinary, with reference to the unpar- with coxa spined on margin of alate posteromesial plate nearly alleled quality of preservation. meeting opposite member in midline, with slender erect spine on posteromesial rim of basi-coxaljoint; basis with single stouter ACKNOWLEDGMENTS ventral spine; ischium with row of four stout spines on ventral We are indebted to C. A. Child and especially W. Blow, who ridge, row of smaller spines or tubercles mesioventrally; elongate called the specimen to our attention and provided data on the merus with double row of spines ventrally, lateral row stronger type locality. E. Jarosewich did the mineralogical analysis and but longer mesial row extending to mero-carpal joint, crest of R. E. Gibbons the photographs. The manuscript was read by spines distally on extensor surface and strong lateral spine at F. A. Chace, Jr., R. B. Manning, G. A. Bishop, and W. N. Orr. mero-carpal joint; articles distal to this missing; pereopod 2 with REFERENCES similar coxa; basis smaller, with strong ventral spine; ischium with ventral row of three strong spines, three smaller spines BORRADAILE,L. A. 1903. On the classification of the Thalassinidea. mesioventrally; merus with three very strong ventral spines; Annals and Magazineof NaturalHistory, series 7, 7:534-551. distal elements missing; pereopod 3 with moderately bulbous BR6NNIMANN,P., ANDP. NORTON. 1960. On the classification of fecal and of new forms from and coxa bearing two mesioventral spines, small spines on rim of pellets descriptions Cuba, Guatemala, basi-coxal basis ischium scattered obso- Libya. EcologaeGeologicae Helvetiae, 53:832-842. joint; short; elongate, M. D. 1963. The evolution of the lescent merus with four BURKENROAD, Eucarida,(Crustacea, spines anteroventrally; elongate spines Eumalacostraca),in relation to the fossil record. Tulane Studies in near one in scattered along ventral aspect, two base, middle, Geology, 2:2-17. one subdistal; carpus with three obsolescent spines on extensor DESAINT LAURENT, M. 1979. Sur la classificationet la phylogeniedes surface; distal elements missing; pereopod 4 held over back, Thalassinidae:definitions de la superfamilledes Axioidea,de la sous- bulbous basis with two ventral spines, ischium and merus with famille des Thomassiniinaeet de deux genres nouveaux (Crustacea suggestion of obsolescent rugae, former with row of obsolescent Decapoda).Comptes Rendus Hebdomadairesdes Seancesde l'Aca- spines anteroventrally; distal elements missing; pereopod 5 demie des Sciences, Paris, Series D, Sciences Naturelles,288:1395- 1397. missing; pair of short crestlike sternal plates between coxae of 3 and broad of sternal GLAESSNER,M. F. 1969. Decapoda, p. R399-R533, R626-R628. In pereopods 4; pair plates separated by C. Moore Treatiseon Invertebrate Part narrow fissure between coxae of 4 and 5. Raymond (ed.), Paleontology, pereopods R, Arthropoda4, Vol. 2. Geological Society of America and Uni- of Abdomen with bases of small pleopod 1 present; fragment versity of Kansas Press, Lawrence. pleopod present on left side of segments 3 and 5; elongate basal HUXLEY,T. H. 1878. On the classificationand the distributionof the element somewhat flattened, endopod stouter than exopod, crayfishes.Proceedings of the Zoological Society of London for the drawn into dorsolateral vane. year 1878:752-788. with loss of the distal parts of the append- KENSLEY,B. 1980. Notes on Axiopsis(Axiopsis) serratifrons (A. Milne agesRemarks.--Even and damage to the carapace, the quality of preservation of Edwards)(Crustacea: Decapoda: Thalassinidea). Proceedings of the of 93:1253-1263. this specimen, with replacement by quartz, would demand de- BiologicalSociety Washington, AND G. M. JR. 1988. nethertoni, a new scription. -, SIMMONS, Axiorygma and species of thalassinideanshrimp from Florida(Decapoda: While the of the Axiidae is still in con- genus generic composition Axiidae). Journalof CrustaceanBiology, 8:657-667. siderable confusion (de Saint Laurent, 1979; Kensley and Sim- KEROHER,G. C., ETAL. 1966. Lexicon of geologic names of the United mons, 1988), the present specimen must be placed in Axiopsis, Statesfor 1936-1960, Part3, P-Z, p. 4127. U.S. GovernmentPrinting albeit with some reservation. Configuration of the serrate ros- Office,Washington, D.C., p. 2887-4341. trum and anterior carapace, antennular and antennal peduncles, LATREILLE,P. A. 1803. Historie naturelle, generale et particulibre, des pleon, and telson, all closely resemble the circumtropical type Crustac s et des Insectes.Ouvrage faisant suite aux oeuvresde Leclerc Naturelle species Axiopsis serratifrons (A. Milne Edwards) (Kensley, 1980, de Buffon,et partiedu cours complet d'Histoire redigepar such features as the of C. S. Sonnini,membre de plusieurssoci tts savantes,5:1-406, Dufart, fig. 1). Unfortunately, diagnostic shape Paris. first and second the antennal spine, the chelae of the pereopods, _ 1831. Cours ou de l'HistoireNaturelle des Crus- the and tu- d'Entomologie, and the uropods are missing. Although spination tacksdu Arachnidesdes Myriapodeset des Insectes,etc. Paris,568 p. berculation of the rostrum and anterior carapace are very similar RATHBUN,M. J. 1919. Decapod from the Panama region. to those of A. serratifrons, the spination of the proximal pereo- U.S. National Museum Bulletin, 103:123-184. pods is heavier in A. eximia. Presence of the bases of pleopods SIPLE,G. E. 1959. Guidebook for the South CarolinaCoastal Plain 1 and lack of a genital aperture on the coxa of pereopod 3 Field Trip of the Carolina Geological Society, Nov. 16-17, 1957. indicate that the specimen was a male. First pleopods being Division of Geology, State Development Board, Columbia, South absent in males of Axiopsis (s.s.), this specimen must be placed Carolina,Bulletin No. 24, 27 p. in one of the of of in which 1 SQUIRES,H. J. 1979. Axiopsis caespitosa (Thalassinidea, Axiidae) a groups species Axiopsis pleopod new from the Pacificcoast of Colombia.Canadian Journal of is in the male. This feature, with the elongate species present along Zoology, 57:1584-1591. eyestalks surpassing the rostral apex, is reminiscent of A. caes- pitosa Squires, 1979, from Pacific Colombia, in which the eye- ACCEPTED6 APRIL 1990 stalks are longer than the rostrum and the cornea wider than