Paragloborotalia experienced considerable evolutionary changes through the Oligocene – middle Miocene, particularly a period of accelerated evolutionary turnover (speciation and extinction) across the Oligocene/Miocene boundary and in the earliest Miocene (Figure 5.1). Major evolutionary trends include: 1) originally 4-5 chambers in the final whorl (ancestral condition), to 6 chambers in the mid- to late Oligocene, and finally up to 7 chambers in the early and middle Miocene; 2) radial spiral sutures through the mid Oligocene (Zone O5; ancestral condition), appearance of slightly curved spiral sutures in the late Oligocene (Zones O6-O7), to more strongly curved spiral sutures in some taxa in the early Miocene (Zone M1) – a trend also noted by Keller (1981); and 3) broadly rounded peripheral margin through the mid-Oligocene (Zone O5; ancestral condition) to some taxa with subacute margins in the late Oligocene and early Miocene. Species of Paragloborotalia range in size from small (0.35 mm) (e.g., Spezzaferri, 1994; Wade and others, 2007, 2016). [Leckie et al. 2018]

Kennett and Srinivasan (1983) erected Jenkinsella (type species siakensis) as a subgenus of Globorotalia, for low trochospiral forms with globular to subglobular chambers, a rounded peripheral margin, lacking a distinct carina, with an umbilical-extraumbilical aperture bordered by a rim. Jenkinsella included opima, semivera, siakensis, bella, mayeri and acrostoma. Paragloborotalia was erected by Cifelli in 1982 and therefore has seniority over Jenkinsella, which is here considered a junior synonym. [Leckie et al. 2018]

Paragloborotalia is distinguished from Parasubbotina by a slower rate of chamber growth and inflation, more embracing chambers, and generally more heavily encrusted test. [Leckie et al. 2018]

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