New Records of Decapods in Pirabas Formation (Miocene), Pará State, Brazil
- 1. Laboratório de Paleontologia, Universidade Federal do Pará, Brazil
Abstract
This work deals the systematic study of the decapods from Pirabas formation (Lower Miocene) at Pará state. Herein are present the first records of the species Piloslambrus guerini [1], Portunus (Portunus) oblongus Rathbun, [2] and Palaeopinnixa porornata [3].
Citation
de Araújo Távora V, Dias JJ (2016) New Records of Decapods in Pirabas Formation (Miocene), Pará State, Brazil. Ann Aquac Res 3(2): 1019.
Keywords
• Decapoda crustaceans
• Miocene
• Pirabas formation
• Brazil
INTRODUCTION
The story of study of fossil decapod crustaceans allow to recognize high specific diversity in some regions of the world. The Miocene record present twenty-seven genera in the paleotropical region at localities in Brazil, Venezuela, Trinidad, Barbados, Ecuador and Peru, time of considerable interchange of taxa between the Southern and Northern hemispheres. Decapod crustaceans records in the Pirabas Formation was initially made by Beurlen [4] and according to Távora et al. [5], 40 different species are recognized at the biggest expositions of this lithostratigraphic unit. This paper deals with systematic studies on three specimens deposited in the paleoinvertebrates collection at Museu de Geociências- Universidade Federal do Pará (MG/UFPa), from the Atalaia beach, Salinópolis city (0º 36’ 5” S, 47º 18’ 48” W), Aricuru district, Maracanã city (0° 42’ 10” S, 47º 30’ 43” W) and B-17 Mine, Capanema city (1º 02’ 47” S, 47º 9’ 26” W), Pará state (Figure 1).
MATERIAL AND METHODS
Carapace measurements are given as carapace width (cw) and carapace length (cl) adopted by Tan and Ng [6]. The analyzed samples were carried out by a Leika S6E binocular microscope, with a precision caliper for obtaining measurements. Photographs were obtained by Sony DSC-HX1digital camera.
Geology
Pirabas Formation [7], with broadly outcrops along northeastern region of the Pará, Maranhão, and Piauí states, provides some of the best marine Cenozoic paleontological occurrences in Brazil. The Pirabas Formation- type location is the Pirabas River estuary, next the Salinópolis city, northeastern of Pará state in the Bragantina platform east of Salinas County in Pará state [8]. The Pirabas Formation consists of richly fossiliferous limestones that indicate a warm, shallow marine depositional environment where lived foraminifera, ostracods, porifera, corals, bryozoans, bivalvs, gastropods, cephalopods, decapoda and cirripedia crustaceans, echinoderms, fishes, reptiles and mammals all of Lower Miocene age [9,10,5,11].
RESULTS AND DISCUSSION
The systematic classification, descriptions and nomenclature follow the proposal used in this paper and the essential terminology, is mainly based on Glaessner [12,13], Tan and Ng [14], Rathbun [2,14] and Collins and Morris [9]. In addition other complementary bibliography was used to complete the study.
CONCLUSIONS
During the Oligocene and Miocene, Atlantic, Caribbean and Pacific waters were united, and the Circum-Tropical Marine Current generally drifted westward. This scenario favored the dispersion and evolution of the portunids and others decapods [15]. The majority of decapods reported in cenozoic strata of Caribbean, Atlantic and Pacific displayed a tethyan diastribution pattern during their history. The abundance and diversity of portunids taxa specially from the Oligocene and Miocene is related to environmental preferences mainly in temperatute and substrate composition, present in Caribbean region [15]. The three species recognized in this research confirm the affinity of the Pirabas formation with the others synchronous litostratigraphic units of the Caribbean region mostly with paleocarcinofaune recorded in Dominican Republic, Trinidad and Panama.
