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Species / Antarctodarwinella Austerocallosa

Antarctodarwinella Austerocallosa


Original Diagnosis

  • "Medium-sized, robust, subglobose Antarctodarwinella with at least 4 weakly angled to gently rounded whorls: last whorl bicarinate with strongly projecting wing, ornamented with poorly developed tubercle development, slightly stronger on adapical keel; last whorl with sinuous growth rugae, stronger near wing and more spaced on older whorls; adapical or posterior sinus angle approximately 52.5; callus development pronounced, partially enveloping spire, but only to penultimate whorl; distinguished from type species, A. ellioti Zinsmeister. 1976, in having a narrower less globose shell, stronger tubercle development, higher spire, and broader aperture."

Original Description of Antarctodarwinella austerocallosa by, Stilwell, Zinsmeister & Oleinik, 2004:

  • "Shell moderately sized for genus and family (up to 35 mm high), semi-globose, thick and robust, low to moderately elevated spire of at least 4 compressed, weakly angled to gently convex, strongly ornamented whorls; protoconch paucispiral, smooth, only partially preserved in available material; spire angle variable from approximately 62 to just over 80; whorl inflation rapid, especially from penultimate to last whorl; sutures encroaching on succeeding whorls, moderately declivous; last whorl capacious, well-inflated with diameter of last whorl just under height of shell; last whorl bicarinate with projected wing, strongly ornamented with rugose, sinuous, varix-like growth increments, posterior or adapical sinus angle ~52.5; moderately spaced, rather blunt, axially extending tubercles, present only on poorly developed carinae that are 5 mm apart, and with interspaces smooth; growth increments closer spaced on last whorl, especially more bunched on wing, compared to more spaced ones on older whorls; last whorl with distinct digitation, that is partially truncated to weakly convex and rounded on the distal portion of wing abaxially; spire whorls with sparse sculpture apart from 10-12 weakly developed, only slightly axially extending, tubercles that commence on antepenultimate whorl; last whorl with extensive callus that encroaches on earlier whorls, extending completely over penultimate whorl, but does not completely envelop the spire, still creating a subglobose outline; fasciole forms a moderately developed low ridge on the abapical part of the last whorl; aperture moderately small, sublenticular to narrowly subovate with distinct raised callus pad extending to the parietal region, becoming slightly narrower at poorly developed canal; columella very gently curved, especially in the parietal area; outer lip thickened."

Locus typicus: Seymour Island, James Ross Island group, Antarctic Peninsula, Antarctica

Stratum typicum: Danian, Paleocene

Dimensions Holotype; Coll. USNM no. 511856: height 35.5 mm. diameter of last whorl including wing 30.5 mm;


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