Ordovician – Devonian
Heterotrypidae is an extinct family of colonial epifaunal suspension feeders
Description of the Family
- Zooarium flabellate
- Zooarium can be incrusting or massive
- Zooecia angular
- Diaphragms straight with no cystiphragms
- Zoarial walls fused
- Few to no mesopores
- Well defined acanthopores
Treatise on Invertebrate Paleontology (1953):
- Zoarium typically erect flabellate but also incrusting to massive. Zooecia angular, with straight diaphragms and no cystiphragms; walls fused but retaining light colored dotted or lined central band. Mesopores few; acanthopores well-defined, commonly large.
- The meager development of this family in the Russian strata seems upon first thought quite unusual, considering the abundant American representation, but a study of the generic distribution offers an explanation for this disparity. Species of Heterotrypa are quite abundant in the various Trenton and Cincinnatian formations of North America but are absent entirely from strata holding the Black River and other Atlantic faunas. They also have not been discovered in European rocks. Dekayella, according to present knowledge, has its origin in a Black River species, D. praenuntia, common to both continents. In later times, representatives of the genus spread to other faunas so that Dekayella lost its value as a strictly Atlantic type. The same is true for Stigmatella and Leptotrypa, both of which have identical Russian and American representatives in Black River time. Cyphotrypa is represented in the Black River by a few species, but its greatest specific development is in faunas of later age, restricted so far as known, to the North American interior seas. Dekayia, Petigopora, and Atactopora are known only in the faunas of late Trenton and Cincinnatian time. With more research into the Russian Heterotrypidae, it is, of course, probable that the above notes will require modification, but it is believed that the following fact will remain unchanged, namely that the Baltic forms belong to the generic types identical with those highly characteristic of the American Black River and other North Atlantic faunas.
- The Heterotrypidae are amalgamate Trepostomata differing from the Monticuliporidae in having straight diaphragms instead of the curved cystiphragms. Clearly defined, frequently large, typical acanthopores are developed in every member of the family. Although the walls of adjoining zooecia are fused, this double wall persists as a distinct but thin unit which has a clean-cut individuality, as shown in sections. The other two families of the Amalgamata differ from the Heterotrypidae in just these two respects. Both the Batostomellidae and the Constellariidae have diaphragms instead of cystiphragms, thus differing from the Monticuliporidae, but the first mentioned has thick walls with a number of them so fused together that the individual wall common to adjacent zooecia is not clearly distinguishable. The Constellariidae differs from all the Amalgamata families in the nature of its acanthopore, which is small and granular.
- Although the family differences mentioned above are few and apparently slight, they are known from the study of a host of species to be fundamental and of as great value as more detailed discriminations founded upon living forms.