Blanca E. Buitrón-Sánchez

The Echinoderms of Mexico: Biodiversity, Distribution and Current State of Knowledge

Mexico is one of the most biodiverse countries on the planet. Knowledge of echinoderm diversity in Mexico started in the XIX Century with Louis Agassiz in 1841. Currently, 643 species of echinoderms are known from Mexico, with Class Ophiuroidea the richest (197 species); Class Asteroidea follows with 185 species, then Class Echinoidea with 119 species, Class Holothuroidea with 113 species, and Class Crinoidea with 29 species. The Mexican deep sea has been little studied, and most expeditions covering this area have been made by institutions in other countries where a great amount of information is deposited but access to it can be difficult. It is necessary to have available catalogues of the Mexican echinoderms with information on their biology, ecology, distribution, and fisheries, in order to facilitate access to information, and promote further studies on the echinoderms of Mexico. Fossil echinoderms are present in the sedimentary basin of Mexico and thus have potential practical use as paleoecological indicators, complementing stratigraphic studies. Although taxonomic studies have resulted in a rather large species list, ecological, life history, and other studies are scarce. Studies on sea cucumber aquaculture in Mexico have not yet started, in spite of the high market value of these animals and their detritivorous habit which makes them attractive for cultivation. It is recommended that aquaculture studies be undertaken. These and other suggestions for advancement of the knowledge and sustainable utilization of echinoderms in Mexico are discussed in the present chapter.

A late Atokan regional encrinite (early late Moscovian, Middle Pennsylvanian) in the Sierra Agua Verde, Sonora state, NW Mexico

Abstract In the Sierra Agua Verde, central Sonora state, NW Mexico, the La Joya Formation exhibits an alternation (100 m thick) of calcareous siltstone and fossiliferous limestone with nodular cherts. This latter contains an abundant and diverse late Atokan (i.e. Podolskian = early late Moscovian, Middle Pennsylvanian) fossil assemblage composed of phylloid algae, fusulinids, chaetetids, tabulate corals, gastropods, fenestellid bryozoans, spiriferid and productid brachiopods, crinoids and conodonts. The crinoidal beds constitute a good example of a regional encrinite. They include several species of the parataxonomic stem form-genera Cyclocaudex, Cyclocrista, Heterosteleschus, Mooreanteris, Pentagonopterix, Preptopremnum, Cycloscapus and Pentaridica. Their preservation indicates the combination of preburial decay on the sea floor and post-burial decay within the sediment. The high degree of silicification of the crinoids indicates that they were possibly associated with siliceous organisms (Porifera?), not preserved in the assemblages. The studied thanatocoenosis is typical of tropical shallow seas, and reveals strong biogeographical affinities with the assemblages of the midcontinental and southern regions of the USA. Particularly, the Atokan crinoids of central Sonora are similar to those from Kansas and Texas, confirming the close palaeogeographic connection of southern USA and northern Mexico during the Middle Pennsylvanian.

PENNSYLVANIAN AND MISSISSIPPIAN PLURICOLUMNAL ASSEMBLAGES (CLASS CRINOIDEA) FROM SOUTHERN MEXICO AND A NEW OCCURRENCE OF A COLUMN WITH A TETRALOBATE LUMEN

In a series of papers on Paleozoic stratigraphy and paleontology in southern Mexico, Buitron and colleagues (Buitron, 1977; Velasco De Leon and Buitron, 1992; Buitron et al., 1987; Villasenor et al., 1987; and Esquivel-Macias, 1996) utilized the crinoid pluricolumnal taxonomy of Moore and Jeffords (1968) to help establish a Pennsylvanian age for the lower Santa Rosa Formation, the del Monte Formation, and the upper Patlanoaya Formation. Since 1968, crinoid pluricolumnal taxonomy and the biostratigraphic utility of pluricolumnals has received very little attention in North America. Whereas the biological classification of crinoids is vested primarily in attributes of the crown, these papers illustrated the biostratigraphic utility of crinoid columnals and pluricolumnals where crinoid crowns are not recovered. Indeed, this was the intent of R. C. Moore, when he embarked on his studies of columnals and pluricolumnals (Moore et al., 1968; Moore and Jeffords, 1968; and Jeffords and Miller, 1968). In this study, previously described Paleozoic crinoid columnals and pluricolumnals from southern Mexico are summarized, and a distinctive pluricolumnal type with a circular column and a tetralobate lumen is reported from the Patlanoaya Formation near San Salvador, Puebla State. Remarkably, these Pennsylvanian columnals record yet another striking example of convergent evolution, where a columnal with a tetralobate lumen developed accessory canals. This note highlights the biostratigraphic utility of isolated crinoid pluricolumnals where they are among the only fossiliferous remains available. #### Pluricolumnals from Mexico To our knowledge, the first report of Paleozoic crinoids from Mexico was by Buitron (1977) who recognized Cylindrocauliscus fiski ? Moore and Jeffords, 1968, and Lamprosterigma mirificum Moore and Jeffords, 1968, from the lower Santa Rosa Formation in Chiapas State (Table 1). These pluricolumnal taxa were reported, respectively, by Jeffords and Miller (1968) from the Desmoinesian Mingus Shale in Texas, USA, and the …

The late Atokan (Moscovian, Pennsylvanian) chaetetid accumulations of Sierra Agua Verde, Sonora (NW Mexico): composition, facies and palaeoenvironmental signals

Abstract The La Joya Formation of the Sierra Agua Verde, Sonora (NW Mexico) is late Atokan in age, equivalent to the early late Moscovian (Podolskian) and fusulinid biozone A3. In this alternance of cherty limestones and thin shaly beds, fusulinellid or anchicodiacean (‘phylloid algae’) wackestones-packstones and crinoidal rudstones-grainstones are the predominant microfacies, but chaetetid boundstones are conspicuous. These chaetetid occurrences of the Sierra Agua Verde are compared with the accumulations of Arizona, Texas, Kansas and Nevada (USA), and the Cantabric Cordillera (Spain). In Sonora, the environments with chaetetids were quiet, and located below wave base. Shallower facies with staffellids and Komia generally top the chaetetids. Because of the associated micritic deposits, the chaetetids have inhabited probably a soft or firm substrate. As a result of the disphotic-aphotic reconstructed environments, the possible symbionts of the chaetetids are more probably heterotrophic bacteria than autotrophic algae. The most comparable ecological conditions exist in the Atokan Marble Falls Formation of central Texas (USA). Chaetetids are not mentioned in the southern suspect terranes of Mexico, but were possibly present because these regions were located along the probable migration way to Peru, the southernmost area where Pennsylvanian chaetetids are known.

Two Lower Cretaceous (Albian) Fossil Holothurians (Echinodermata) from Tepexi De Rodriguez, Puebla, Mexico

Abstract Two new genera and species of well-preserved fossil holothurians are described from the Lower Cretaceous (Albian) of Tepexi de Rodriguez, Puebla, central Mexico. Parapsolus tlayuensis is a psolid, and Paleopentacta alencasterae is a cucumariid. Paleopentacta alencasterae is the first complete holothurian fossil known to have two types of body wall ossicles preserved. The presence of the families Psolidae and Cucumariidae suggests that the local habitat was a hard substrate. The two holothurian species described here are interpreted as shallow water-suspension feeding species.

An occurence records database of Irregular Echinoids (Echinodermata: Echinoidea) in Mexico

Abstract Background Research on echinoderms in Mexico began in the late nineteenth century. We present a dataset that includes the taxonomic and geographic information of irregular echinoids from Mexico, housed in four collections: 1) Colección Nacional de Equinodermos “Ma. Elena Caso Muñoz” from the Instituto de Ciencias del Mar y Limnología (ICML), Universidad Nacional Autónoma de México (UNAM); 2) Invertebrate Zoology Collection, Smithsonian Museum of Natural History, Washington, D.C., United States of America (USA); 3) Invertebrate Collection, Museum of Comparative Zoology, University of Harvard, Boston, Massachusetts, USA and 4) Invertebrate Zoology, Peabody Museum, Yale University, New Haven, Connecticut, USA. New information A total of six orders, 17 families, 35 genera and 68 species are reported, 37 distributed in the Pacific coast and 31 in the Atlantic coast, none of them was found in both coasts. The most diverse region is the Gulf of California (S=32); the most diverse order is Spatangoida with 31 species reported in mexican waters.