Extinct and extant sand dollars (Clypeasteroida: Echinoidea) from Uruguay

Area of Science:

• Paleontology
• Marine Biology
• Echinoderm Paleobiology

Background:

• Uruguayan fossil record of sand dollars (Mellitidae and Monophorasteridae) provides insights into past marine conditions.
• Recent sand dollar species in Uruguay represent the southern extent of their known geographic ranges.

Purpose of the Study:

• To summarize information on Uruguayan sand dollars from the Recent, Pleistocene-Holocene, and Miocene epochs.
• To investigate factors limiting the distribution of Recent sand dollars in Uruguay.
• To establish the phylogenetic relationship between Monophorasteridae and Mellitidae.

Main Methods:

• Literature review and synthesis of existing paleontological and neontological data.
• Analysis of geographic distribution data for Recent and fossil sand dollar species.
• Phylogenetic placement of Monophorasteridae relative to Mellitidae.

Main Results:

• Recent sand dollars (Encope emarginata, Mellita quinquiesperforata, Leodia sexisperforata) are at their southern distribution limits in Uruguay.
• Lower temperatures and the Rio de la Plata salinity barrier are potential factors controlling Recent sand dollar distribution.
• The extinct genera Monophoraster and Amplaster (Monophorasteridae) showed peak diversity in Uruguay during the warmer Miocene.
• Monophorasteridae is identified as the basal sister group to the Mellitidae.

Conclusions:

• Environmental factors like temperature and salinity have historically shaped sand dollar distribution in Uruguay.
• The Miocene provided favorable conditions for the diversification of Monophorasteridae in the region.
• Understanding these distributions aids in reconstructing past marine environments and evolutionary relationships.