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A violent storm has left a wealth of sea life strewn over a coral reef in what is now the Solnhoven limestone formation. Several species of pterosaurs (Pterodactylus, Rhamphorhynchus, and Germanodactylus) circle overhead. An Archaeopteryx has flown out and is defending the carcass of a small shark from a pair of small pterosaurs (Scaphognathus). (Post storm cleanup is a reconstruction of a Jurassic scene by Gary Bloomfield. Use of this image is protected by copyright. For a larger view, click here.)

Plate Tectonic Reconstructions

Jurassic* ammonites and dinosaurs made a huge comeback after their near extinction at the end of the Triassic. Reptiles remained the dominant land animals even after their massive losses to extinction at the end of the Triassic. Dinosaurs grew larger, with the largest saurichians appearing in the Upper Jurassic. The other main dinosaur group, the ornithicians, makes their first appearance in the Jurassic. The first bird fossils and flying pterosaurs showed up in the fossil record.

The Pangaea supercontinent began breaking up during the Jurassic, with the birth of the Central Atlantic Ocean at the end of the Middle Jurassic. By the end of this Period most of today's continents were delineated, though differently located. Climate was warm on land since the continents were located more equatorially. Sediments rich in organic materials later became sources for today’s petroleum.

*Jurassic derives from Alexander von Humboldt's use of the term “Jura Kalstein” for carbonate deposits in the Jura region of Switzerland in 1799.

Jurassic Animal (Metazoan) Fossils
Crustacea (ToL: Arthropoda<Ecdysozoa<Bilateria<Metazoa<Eukaryota)
	Although the trilobites had vanished, the arthopods were well represented in the oceans by crustaceans. These included shrimp, lobsters, and crabs (Decapoda) such as Eryon arctiformis.
Echinoderms (ToL: Echinodermata<Deuterostomia<Bilateria<Metazoa<Eukaryota)
	Brittle stars (Ophiuroidea) are represented by specimens of Geocoma elegans on a rock slab.
	Sea urchins (Echinoidea [sea urchins and relatives]) diversified during the Jurassic. Cidaris coronata is an example.
Vertebrates (ToL: Vertebrata<Chordata<Deuterostomia<Bilateria<Metazoa<Eukaryota)
	Bony Fish (Osteichthyes): Ray-finned fish, such as Leptolepis sprattiformis, diversified beginning in the middle of the Mesozoic, and have continued to diversify up to the present.
	Dinosaurs (Dinosauria [Birds and Dinosaurs]). Of the two major dinosaur groups, the ornithicians are represented by a skull cast (a Hypsilophodont  Othniella rex also known as “Nannosaurus rex”). The other dinosaur fossils may be of either ornithician or saurichian origin: A polished slab of dinosaur bone. A chunk of dinosaur bone. Gastroliths, stones used by dinosaurs to help grind their food. Both dinosaurs and birds, their modern descendants, used a crop filled with stones to help break down their food into small particles to aid digestion.
	Birds (Aves<Dinosauria [Birds and Dinosaurs]<Reptilia). A cast of a fossil of the earliest known bird,Archeopteryx lithographica, represents the dinosaur line which led to modern birds.
Mollusks (ToL: Mollusca<Lophotrochozoa<Bilateria<Metazoa<Eukaryota)
	Bivalves (Bivalvia) diversified in the Jurassic. Oysters, such as Gryphaea arcuata and Inoceramus mucronata, appeared. A clam, Buchia acutistriata (fossil and negative cast) is also displayed.
	Gastropods (Gastropoda): The museum has a single specimens with some very small snails, Valvata scabrida, on display.
	Cephalopods (Cephalopoda): Ammonites underwent a remarkable recovery in the Jurassic, and continued to diversify until their extinction at the end of the Mesozoic Era. Specimens include a plate of Dactylioceras sp., and individuals of: Dactylioceras tennicostatum, Praeparkinsonia garantiformis, and Acanthopleuroceras valdani. The squid-like belemnoids peaked during this Period. We have two specimens of the tusk-shaped ballast from Pachyteuthis densus and an unidentified species.
Brachiopods (ToL: Brachiopoda<Lophotrochozoa<Bilateria<Metazoa<Eukaryota)
	Brachiopods, such as Rhynchonella sp., maintained themselves as a minor group.
Jurassic Plant Fossils
Vascular Plants (ToL: Embryophytes [land plants] <Green Plants<Eukaryota)
	Cycadeoids (relatives of todays cycads), short trees with palm-like branches, were abundant in dryer areas. A piece of Cycadeoidea bark in shown.

The engravings are from Dana, James D. (1870) Manual of Geology and Le Conte, Joseph (1898) A Compend of Geology.

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Last modified 29 January 2007 | ©1998, HSU NHM