A Sebecid Crocodyliform From Miocene Neogene Cuba?

Enigmatic crocodyliforms from the early Miocene of Cuba

Authors:

Brochu et al

Abstract:

Early Miocene deposits from the Domo de Zaza locality, in the south-central Cuban province of Sancti Spiritus, preserve crocodyliform remains, including compressed serrated teeth closely resembling those of South American sebecids. Fragmentary cranial and mandibular material is more difficult to assess. Referral to any other post-Paleogene crocodyliform known from the Western Hemisphere can be ruled out, and phylogenetic analyses are unable to pinpoint its relationships. Similarities can be found with planocraniids, including ventrally oriented and mediolaterally expanded orbital surfaces, but the morphology of the quadrate is inconsistent with a planocraniid affinity. A sebecid in the Miocene of Cuba would be congruent with evidence from other vertebrates suggesting extensive dispersal between the Greater Antilles and South America during the Neogene, and it would be the first Neogene record of the group outside South America. The other crocodyliform may indicate the presence of an endemic West Indian lineage not closely related to any contemporaneous group. It is also consistent with extant Crocodylus arriving in the Neotropics within the past 5–10 million years.

The Earliest Cambrian Reef Builders Appear to Have Been Metazoans...Which Later Went Extinct

TALES FROM THE CRYPT: EARLY ADAPTATION OF CRYPTOBIONTIC SESSILE METAZOANS

Authors:

Hong et al

Abstract:

Cryptic ecosystems of modern and ancient reefs contain substantial amounts of biodiversity. It remains uncertain, however, when and how metazoans adapted to such space. Early Cambrian reef systems witnessed the rise and fall of the earliest known cryptic sessile metazoans. Subsequent Middle Cambrian to Early Ordovician microbial-dominated reefs were generally devoid of true frame-building metazoans, as well as cryptic sessile fauna. The Early Ordovician microbial–siliceous sponge patch reefs of the Dumugol Formation, Korea represent one of the oldest in situ spiculate sponge-bearing cryptic communities exploiting intraskeletal cryptic environments. Less than half of these small millimeter- to centimeter-scale crypts contain low-diversity sessile cryptic assemblages of spiculate sponges and microbialites. The cryptic sponges that attach to the walls of the cavities or on top of internal sediments do not show any skeletal distortion at their contacts with host organisms. The spiculate sponges occur both in open spaces as well as in crypts, and are interpreted to be pioneers of intraskeletal crypts after the death of the cavity-providing organisms. The behavior of occupying transient cryptic habitats is interpreted as an incipient stage of sessile metazoan adaptation to a cryptic space by an opportunistic member of the epibenthic community. This resulted in the extension of the open surface community into crypts which occurred far in advance of the eventual establishment of obligate cryptic forms. The present study provides a critical link for establishing the origin and evolutionary history of early cryptic sessile metazoan adaptation.