Palæos: Mesozoic		Early Cretaceous
CRETACEOUS PERIOD		Berriasian

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Introduction to the Berriasian

The Berriasian is the first Age of the Cretaceous.  In fact, it includes territory which historically has been placed in the Jurassic Period -- specifically, the later parts of the Portlandian (European) and Volgian (Russian) stages.  In addition, parts of the important Yixian Formation in China, which were formerly treated as Late Jurassic, have been redated as Berriasian or even Valanginian.  What with the general uncertainty surrounding the base of the Cretaceous, the Berriasian has been confusing to students and unpopular with geologists, who tend to revert to regional nomenclature when they think they can get away with it. 

By the Berriasian, East Gondwana (India, Australia and Antarctica) had separated cleanly from West Gondwana (Africa and South America); and, by the end of the Age, India was beginning to break from East Gondwana.  The Tethys had long since split the Gondwanan lands from the Northern lands, although the situation in the Caribbean Basin was complex.  The Pacific Plate  was growing, but still quite small, and the entire western margin of North and South America was fringed with volcanic island arcs.  Zharkov et al. (1998).  

The cooling trend of the Late Jurassic continued into at least the middle of the Berriasian, and the poles may have borne small permanent ice caps, with glaciers at higher elevation in East Gondwana. The Atlantic and Ural connections between the Tethys and the northern sea were still well in the future, so that the Middle latitudes of the Northern hemisphere were thermally isolated and quite cool, at least by Mesozoic standards.  Chumakov (2003).  

Most of the characteristic life forms of the Cretaceous had not yet evolved or were insignificant, including angiosperms, mosasaurs, therian mammals, hadrosaurs, rudists, calcareous plankton and planktonic foraminifera.  Dinosaurs were represented by Brachiosaurus, Camptosaurus, Iguanodon, and a number of weird and poorly known transitional forms such as Cetiosaurus, Altispinax, Emausaurus, Megalosaurus, and Stenopelix.  Teleost fish were present, but not yet in their Cenozoic forms, and the dominant marine reptiles were Cimoliasaurus and  Cryptocleidus.  

Image credits: Camptosaurus  from the College of Eastern Utah Museum site.  Map from the American Association of Petroleum Geologists site.

Links: The Plesiosaur Site - Stratigraphy; DinoData Dinosaurs Timeperiods Berriasian; anrepeap.  

ATW050219.  Text public domain.  No rights reserved.

Berriasian Life

Arthropods

Generally speaking, the Cretaceous was not a good time for arthropods (although it is not easy to be certain, because of the usually miserable fossil record).  The clear exception are the Crustacea who produced both lobsters and shrimp at some point in the earliest Cretaceous.  Sadly, such essential condiments as butter, tomato sauce, and horseradish were not yet available in the Berriasian.  

Chelicerates nearly became extinct in the Cretaceous, at least by comparison to their large diversity in the Paleozoic and Cenozoic.  However, spiders were present and the remains of a number of orb-web weavers are known from the Berriasian.  These spiders may have benefited from the large number of flying insects.  The flying insect jobs were dominated by Diptera.  In fact, it was an age of flies.  Since many modern neopteran insect groups had not yet become important, flies occupied a large number of niches in which they are now marginal, including the job of nipping at vertebrates (absent gnats, midges and mosquitoes).  Mostovski et al. (2003).  When angiosperms arrived later in the Neocomian, it was these flies with suctorial mouthparts which first evolved as pollinators.  

Two important clades of insect recyclers are first found in the Berriasian.  The first of these are the Scarabaeoidea, the stag, scarab and dung beetles.  They are probably of Jurassic origin, but diversified in the Berriasian.  Krell (2000).  A far more important development was the evolution of termites (Isoptera), which evolved from the ancient cockroach lineage (Blattaria) during, or just before, the Berriasian.  Mayhew (2002).  

Bear in mind that wood recycling had been handled almost exclusively by fungi since the Mississippian.  The fungi do a very thorough job, but they're slow.  Lignin is a fiendishly complex molecule, and generates an amusing variety of toxic phenols if it isn't digested in just the right way.  Termites can't actually digest lignin themselves, but the termite gut is a very complex ecosystem which plays host to an entire battery of bacterial and protist symbiotes which cooperate to get the job done rather quickly.  C.f. Oxymonadida (one of the main protist groups involved in this industry).  The advent of termites would likely have changed the entire forest food chain.  Prior to termites, dead or fallen trees would have remained in place for many years as they were slowly consumed by rot.  Termites recycle the nutrient content of wood much faster and convert it into insect biomass.  This would not only permit faster recovery of woodlands from storm, fire and (perhaps) sauropod damage, but would open up vast new opportunities for small insectivores.  One might suspect that the rapid spread of the opportunistic and aggressive angiosperms and the diversification of insectivorous therian mammals just after the Berriasian was not a coincidence.  Thus, we may have mutant cockroaches to thank for the existence of both ourselves and our main food supplies.    

Image Credits: termite from Fossilmall.com.  Pseudosimilium from Mostovski et al. (2003).

ATW050220.  Text public domain.  No rights reserved.