Degree Name

Master of Science (MS)

Semester of Degree Completion


Thesis Director

Frederick R. Schram


A Mississippian syncarid from the Heath shale, Squillites spinosus Scott, 1938, is redescribed and a discussion of some aspects of Syncarid phylogeny is given. Modern Syncarid biogeographical distribution is discussed and an analysis of these zoogeographical patterns is provided. A strange animal, Crustacea (incerta sedis) from the Heath shale is described in as far as is possible.

In 1971, Dr. Richard Lund of the University of Pittsburgh while searching for fossil fish in the Upper Mississippian Heath Shale of Montana found the associated remains of fossil crustaceans. Two locations were involved, T14 N R20E sec. 28, Fergus County, Montana, 2 miles south and 6 miles east of Heath, and 2¼ miles south of Heath, Fergus County, Montana. The crustacean fossils were found in a black paper shale horizon which averaged about 8 inches in thickness above which was non-fossiliferous limestone grading within inches into salt-clast lime. Below the black shale was a sequence of non-fossiliferous limestones about 4 feet thick which were followed by a conodont horizon which was very fossiliferous.

The black shale in which the crustaceans were found contained many fish, some marine, some fresh water, and most of uncertain habitat. Also present were conchostracans, unidentifiable ostracods and Spirorbis sp. (Lund, personal communication).

Scott (1935) states that the Heath Formation forms the upper beds of the Big Snowy Group, Chesterian, Upper Mississippian. He found in the basal zone of the Heath Formation the index brachiopod Leiorhyncus carboniferum along with an abundance of conodonts. Other fossils he lists as found in the Heath Formation are the brachiopods Productus ovatus, Productus inflatus, Echinochoncus sp., Spirifer sp., Chonetes chesteriensis, Composita subquadrata, Lingula sp. and Orviculoidea sp. The molluscs are represented by Cypricardella sp., Trepospira sp. and Aviculipecten sp. Also found is the Ostracod Cytherella sp. as well as many conodont assemblages. Scott (1938) described Squillites spinosus as a "strange stomatopod" which he found in the black Heath Shale. This animal was later reassigned by Brooks (1962b) to the Superorder Syncarida. Another Syncarid found in the Heath is Paleosyncaris dakotensis Brooks, 1962b, found in the Heath Formation of North Dakota.

This paper will present the results of study of two of the crustaceans of the Heath shale. A redescription of Squillites spinosus Scott, 1938, will be given and a new crustacean will be described in as far as it is known.