Contributions to Zoology, 72 (2-3) 79-81 (2003)
SPB Academic Publishing bv, The Hague
Early Cretaceous decapod Crustacea from the Neuquén Basin, west-central
Argentina
Maria+Beatriz Aguirre-Urreta
Departamento de Ciencias Geológicas, Universidad de Buenos Aires, Ciudad Universitaria, 1428 Buenos
Aires, Argentina
Keywords:: Crustacea, Decapoda, Cretaceous, Argentina
Abstract silty shales and coquinas of the Agrio Formation
The (Early Valanginian-Early Barremian). gypsum
Marine ofthe Basin of west-central beds of the Huitrin Formation indicate the deposits Neuquén Argen- regres- tina (southern South America) are richly fossiliferous; its Meso- sion of the Pacific sea during the Barremian zoic invertebratefaunas, represented mostly by molluscs, have (Legarreta & Uliana, 1991). been extensively studied since the nineteenth century. How-
Cretaceous far less ever, Early decapod crustaceans are known,
although part of the systematic framework has been published
The aim of the is (Aguirre-Urreta, 1989). present note to pro- Decapod fossils vide updated information based on ongoing research into the
in systematics and taphonomy of this crustacean group the The fossils studied for the present note are from Neuquén Basin. the Agrio Formation. From north to south, locali-
ties are: 1 - Cerro La Parva, 2 - Cerro Pitren, 3 -
- - Mina San Eduardo, 4 Lonco Vaca, 5 de Introduction Agua
La Mula, 6 - El Salado, and 7 - Rio Agrio (Fig. 1).
Decapod crustaceans from the Neuquen Basin are The Neuquen Basin is a retroarc basin thatextends assignable to the Palinura, Anomura and Astacidea. along the foothills of the Andes from 35°SL to
39°SL, expanding towards the eastern foreland for-
ming a large embayment, where the marine Lower Palinura Cretaceous is represented by a major sedimentary
that cycle encompasses a Pacific marine transgres- In the Basin, the are sion ofTithonian Barremian Neuquen palinurans represented (latest Jurassic) to age. mainly by Meyerella rapax (Harbort), as recognised The Lower Cretaceous sediments in the Neuquen at Cerro La Parva and Mina San Eduardo, in the Basin comprise both marine and terrestrial depos- lower of the Formation (Karaka- its. The portion Agrio marine Tithonian-LowerValanginian is rep- schiceras attenuatus and Viluceras permolestus resented by rich organic, dark shales with calcareous ammonite subzones, late Valanginian). At Cerro nodules (Vaca Muerta Formation, Tithonian-Ber- La Parva specimens are highly abundantand riasian) and thinly laminated limestones (Quintuco pre- served in incomplete calcareous nodules that have Formation, Berriasian-Valanginian). During the and been reworked redeposited at the base of a thin Valanginian a regression occurred, and there was storm deposit. They occur together with ammonites a coexistence of terrestrial and volcaniclastic beds and oysters. The preservation closely resembles that mterbeddcd with marine shales (Mulichinco Forma- recorded by Simpson & Middleton (1985) for Me- tion) and thick carbonate deposits (Chachao For- yerella magna in the Atherfield Clay Formation of mation). A transgressive phase occurred in the late England. Specimens of M. from Cerro La Early Valanginian with the deposition of shales, rapax
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horizons and Fig. I. Composite section ofthe Agrio Formation with the various that have yielded decapod crustaceans, a locality map
scale. ofthe Neuquen Basin (inset). Fossils are not to
M. such the bivalves Anomia Parva arc articulated with the calcareous matrix not on magna, as laevigata
the thus and Aetostreon and an completely enclosing carapace, producing sp., suggested epibcnthic
for this lobster Our material a lateral compression of the fossil. Simpson & Mid- way of life species.
dleton the Ceratostreon be (1985) documented the presence of epizoans shows oyster sp. to common,
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but it whether cannot be determined the oysters palinuran Glyphea rosenkrantzi. At the other level,
settled the while attached on specimens alive, or to the same nodules are reworked and redeposited at
the formed nodules. of already the base a storm deposit.
the death of the the Following animals, preser-
vation ofM. from rapax Cerro La Parva probably
included initial of an stage shallow burial of corpses Astacidea
the to produce incomplete nodules, a relatively
extended of of period exposure nodules on the sea- This is in group represented the Neuquen Basin by floor to allow settlement and growth to adulthood and is known from erymids nephropids. Eryma sp. of Ceratostreon and the and final sp., reworking the Neocomites beds (late Valanginian) and also
deposition of nodules at the base of a At coquina. associated with olcostephanid ammonites (Olco- Mina San Eduardo, specimens are enclosed in their laticosta ammonite stephanus subzone, early Hau-
entirety in flatfish, ovoid, calcareous con- sandy terivian). Hoploparia sp. has been recorded from cretions. this zone as well but is more abundant in the Spiti-
discus riccardii ammonitezone (early Hauterivian).
Their mode of differs. preservation In Eryma sp.,
Anomura the of the is carapace cephalothorax normally pre-
served, as well as isolated chelipeds, both in cal-
This the group is the most abundant in Agrio For- careous nodules and silty shales, but the abdomen mation, being represented by Protaxius sp. With is rarely found. On the other hand, all records of
to Protaxius only chelipeds present, assignment sp. Hoploparia sp. correspond to chelipeds preserved is of the problematic; part material may belong to in calcareous nodules within dark shales.
Protocallianassa. Material has been recovered from
different levels stratigraphic and localities, rang- Acknowledgements ing from the Upper Valanginian at Cerro Pitren to the Lower Hauterivian at Lonco Vaca, Agua de La I am most grateful to Dario Lazo (University of Buenos Aires) Mula, El Salado, and Rio Agrio. The commonest and Peter Rawson (University College, London) for providing state of preservation corresponds to small, near- several specimens for this study. CONICET PID 360/98 and
spherical calcareous nodules with the x 155 thanked for only cheliped UBACYT are financial support.
pair preserved; less often, just one of the chelipeds is preserved. The nodules are invariably embed- References ded in dark shales typical of a calm environmental
setting. Aguirre-Urreta MB. 1989. The Cretaceous decapod Crusta- La However, at Agua de Mula, there are two cea ofArgentina and the Antarctic Peninsula. Palaeontology distinctive levels with nodules yielding Protaxius 32: 499-552.
in the ammonite sp. Hoplitocrioceras gentilii zone Bromley RG, Asgaard U. 1972. The burrows and microco-
of prolites Glyphea a Lower Jurassic (early Hauterivian). Here the specimens are articu- rosenkrantzi, palinuran lated crustacean from Jameson Land, East Greenland. Groenl. and near-complete, with the body parallel to Geol. Unders. Rapp. 49: 15-21. main axis of the nodule. At one level, the nodules, Lcgarreta L, Uliana MA. 1991. Jurassic-Cretaceous marine ovoid in to irregular shape, are preserved in silty oscillations and geometry of backarc basin fill, central Ar- shales and fine sandstones associated with burrowing gentineAndes, Spec. Pubis Int. Ass. Sediment. 12:429-450.
systems corresponding to the ichnogenus Thalas- Simpson Ml, Middleton R. 1985. Gross morphology and the sinoides. mode of life oftwo species oflobster from the Lower Creta- Although nodules were not found to be of ceous England : Meyeria ornata (Phillips) and Meyerella confined to the thalassinoid burrowing it system, Trans. magna (M’Coy). Roy. Soc. Edin. Earth Sci. 76: 203- is most probable that the decapod did indeed in- 215. habit those galleries comparable to the example documented Received: 1 2003 by Bromley & Asgaard (1972) for the April
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