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Fossil Invertebrates

sponges Arborospongia unnamed sponge productid brachiopod conularid

Sponges (and associated fauna)

The sponge Arborispongia (far left) (see Rigby, 1985) is locally abundant. An unnamed sponge (middle left) is much more rare. Scallop-like and mussel-like clams and spiny productid brachiopods (middle right) are frequently found attached to them. Conulariids (far right) are usually also found in association with Arborispongia (See Babcock and Feldmann, 1986). (Click on the fossils for popup enlargements.)

sphenothallus Sphenothallus species one colonial Sphenothallus


Two species of the attached invertebrate Sphenothallus Hall (Hill, 1978) are also common, each species in a different environment. Species 1 (left), a solitary form, is found toward the deeper part of the bay, while Species 2 (right), a branching, colonial form, is an indicator of shallow water. Sphenothallus is known from similar aged rocks in Indiana and Glencartholm, Scotland.

brachiopods and bivalves Lingula Aviculopecten mytiloid

Brachiopods and Bivalves

Occurrences of the inarticulate brachiopod Lingula are localized, as are the occurrences of the few kinds of articulate brachiopods (see Lutz-Garihan, 1985). Scallop-like and mussel-like bivalves, as well as Sphenothallus species 1, are found attached to many things; such as algal fronds (see McRoberts and Stanley, 1989), sponges, a sunken log, and cephalopod shells.

cephalopods orthocone nautiloid coiled nautiloid


Several species of orthoconic (Reticycloceras) and coiled (Anthracoceras) nautiloid cephalopods are abundant. While the shell minerals are usually gone, many specimens preserve traces of internal anatomy. They are indicators of open water marine influence (see Landman and Davis, 1988; Mapes, 1987).

worms worm worm polychaete polychaete polychaete polychaete

Assorted Worms

There are many species of platyhelminth, nemertine, and annelid worms in the fauna (see Schram 1979c). (Click on the fossils to view a popup enlargment.)

fossil arthropods Dithyrocaris Tyrannophontes Bairdops Aenigmocaris Paleolimulus


At least one dozen species of concavicarid, phyllocarid (Dithyrocaris view 1 & view 2), paleostomatopod (Bairdops and Tyrannophontes), and eumalocostracan (Aenigmocaris) crustaceans are known (see Briggs and Rolfe, 1983; Factor and Feldmann, 1985; Hof, 1998; Jenner et al., 1998; Schram and Horner, 1978; Schram, 1979a, 1985). The sole species of horseshoe crab, Paleolimulus, is rare (see Schram, 1979b). Several species of Bear Gulch fish have crustaceans in their guts. Only one tiny trilobite specimen has been found in the Bear Gulch Limestone although they are not rare in adjacent shelly beds of the Heath Formation.


Echinoderms (crinoids, echinoids, asteroids, and ophiuroids) such as Lepidasterella are rare (see Welch, 1984), highly localized, and usually poorly preserved because of the postmortem loss of aragonite from their skeletons.


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