Hartonella, Hussain & Rogers & Blackburn, 2022

Hussain, Rowshi, Rogers, Steven L. & Blackburn, Joel A., 2022, Ovummuridae (calcareous microfossils) from the Much Wenlock Limestone Formation, Shropshire, UK, Palaeontologia Electronica (a 27) 25 (2), pp. 1-24 : 14

Genus HARTONELLA gen. nov.

zoobank.org/ 68D3F0D5-A429-4F3E-9B75-7B99E61B9A01

Derivation of name. After Harton Hollow, Shropshire, UK. The name of the locality the genus was first found from, genus feminine.

Type species. Hartonella oblonga sp. nov., the only species known.

Diagnosis. Elongated oval shaped test comprising of two asymmetrical chambers. The larger dorsal chamber is elongate, oval shaped separated by a pseudo-septum from the ventral oval to hemispherical chamber. The ventral chambers apex can be either smooth or sharp. An aperture is present within the central axis of the posterior of the dorsal chamber. The wall is comprised of calcite tablets that are in a lamellar arrangement.

Remarks. These Ovummuridae specimens do not conform to the specifications of the genera: Minourella , Ovummurus , Arouxina or Samtlebenella because: (1) their chambers are not globular like Minourella or Ovummurus and are elongate and tubular, (2) their chambers are not symmetrical like Ovummurus , (3) they do not exhibit hemispherical chambers around the initial chambers like Arouxina and (4) they do not contain chambers within their walls like Samtlebenella . Therefore, based upon their morphological differences and measurements, a new genus has been established to account for the elongate nature of these variants of Ovummuridae .

The genus is comparable to other microfossils, such as foraminifera; lagenoid forms such as Nodosaria sp. ( Loeblich and Tappan, 1964) have straight chambers similar to these elongate Ovummuridae variants. However, they also have characteristic planispirally coiled or uncoiled chambers which are not observed in Ovummuridae . Nodosariacea comprise uni-multilamellar chambers, and their tests are finely perforated, neither which are distinctive of the Ovummuridae ( Loeblich and Tappan, 1964 and Minoura and Chitoku, 1979). Similarly, foraminifera such as: Earlandia ex gr. minor ( Rauzer-Chernousova, 1948) and Miliolata Nubeculariina Calcivertelloidea: Calcivertella sp. Cushman and Waters, 1928 in cross section can have elongated tubular appearances similarly seen to these ovummurid variants. Although, they share characteristics in their undivided tubular test chambers, Calcivertella sp. walls are porcelaneous, and they have a streptospirally coiled test ( Vachard et al., 2018).

Hartonella is anatomically comparable to chitinozoans, in particular, Conochitinia proboscifera Eiesenack, 1937. They are both tubular and elongated nature. However, unlike the chitinozoans, Ovummuridae are not chitinous, and their tests are formed of calcite tablets.

Stratigraphical range. Lower Silurian (Homerian).