Microeciella Taylor and Sequeiros, 1982

Taylor, Paul D. & Zatoń, Michał, 2008, Taxonomy of the bryozoan genera Oncousoecia, Microeciella and Eurystrotos (Cyclostomata: Oncousoeciidae), Journal of Natural History 42 (39 - 40), pp. 2557-2574 : 2567-2569

Genus Microeciella Taylor and Sequeiros, 1982

Type species. Microeciella beliensis Taylor and Sequeiros, 1982 , Jurassic , Toarcian, Belchite, Spain .

Diagnosis

Colony encrusting, multiserial, unilamellar, sheet-like, initially fan-shaped, generally becoming subcircular, occasionally flabellate, not branching; some species developing marginal subcolonies; all polymorphs fixed-walled with pseudoporous calcified exterior walls. Autozooids simple, tubular, apertures circular or elliptical, more or less regularly spaced, neither connate nor aligned in rows, peristomes moderate in length; terminal diaphragms often present in older zooids. Gonozooids longitudinally elongated, ovoidal, only slightly larger than autozooids, the densely pseudoporous and bulbous brood chamber roof not penetrated by autozooidal peristomes; ooeciopore terminal or subterminal, circular or transversely elliptical, a little smaller than an autozooidal aperture; ooeciostome short, straight, not adnate to an autozooidal peristome. Kenozooids lacking or sporadic.

Remarks

The spot- or sheet-like colony-form of Microeciella enables it to be distinguished from Oncousoecia in which colonies consist of ramifying oligoserial branches with tapered branch edges formed by kenozooids. Autozooidal and gonozooidal morphology are, however, essentially identical in the two genera. Although considerable within-species variability in colony-form has been documented in cyclostomes, especially by Harmelin (1973, 1976), this seldom if ever includes transitions between encrusting colonies with ramifying oligoserial branches and those with non-ramifying, subcircular spot- or sheet-like colonies. Therefore, the use of colony-form to distinguish between Oncousoecia and Microeciella is justifiable given our present state of understanding.

Two Lower Jurassic species from Spain were initially placed in Microeciella , the type species M. beliensis Taylor and Sequeiros, 1982 and M. reflexa Taylor and Sequeiros, 1982 . Subsequently, a few other Jurassic and Cretaceous species have been assigned to the genus: M. duofluvina ( Cuffey and Ehleiter, 1984) and M. pollostos Taylor and Wilson, 1999 from the Middle Jurassic of the western USA, and M. livingstoni Taylor and McKinney, 2006 from the Upper Cretaceous of Alabama. Un-named species of Microeciella have also been recorded from the Middle and Upper Jurassic of Poland ( Hara 2007; Hara and Taylor in review; Taylor in press), while M. matisconensis Walter, 1970 from the French Middle Jurassic also belongs in Microeciella . Reassignment of additional fossil and recent species to Microeciella is probable after the gonozooidal morphology of the numerous species attributed to Berenicea has been established.

Distribution

This genus is known at the present day from both the northern hemisphere (northeast Atlantic and Mediterranean) and the southern hemisphere ( Antarctica and New Zealand), and has a geological range extending back to the Early Jurassic (Pliensbachian).