Conus (Lithoconus) gajensis (Jain, 2014)

 

Description : This is a giant Conus species found in the Kathiawar area in early Miocene horizons in the Gaj Formation. It is well-known for its giant size and local tribal people worship it in their temples. The shell is removed and not seen in any specimen seen in the field. The aperture is straight and is almost the same height as the last whorl. The spire is very small or might be sunken. The protoconch and initial whorls are not preserved. Diameter/Height ratio and basal angle are very high. These characters suggest the subgenus Lithoconus. This species should not be confused with the giant inner moulds of an undescribed species belongs to the family Strombidae. I do not know whether any giant fossils like the present examples have been described in the subgenus Lithoconus previously. Fossils of giant Strombus are embedded in the rock and inner moulds of their initial whorls sometimes give the false appearance of Conus, but they invariably have nodes on the shoulder area. However, in the case the present new species of giant Conus the whorls are smooth and the spire is extremely low to flat (2).

 

Material : Two specimens (outer shell removed). Many specimens observed in the field (2).

Horizons and Localities : Gaj Fm., Ranjitpur Mem., Sec.-I, Bed No. 3, Zone-1, Early Miocene (2)

 

Etymology : This species is named for its occurrence in a wide geographical area in the Gaj Formation in the study area (2).

 

Remarks : This species was mentioned in the old literature just as a passing reference by calling it giant Conus. It is a unique new species distinguished by its giant size, very high D/H ratio and high basal angle. This species is found in abundance and local villagers worship it as God’s auspicious Conch. Untill now no suitable closely comparable form is found in the literature; hence it is assigned to a new species. However, in shape and in its very short spire it is very similar to Conus (Lithoconus) literatus Linnaeus, 1758.

 

 

Herein, we are  reporting for the  first time two large sized gastropods from Early-Middle Miocene  beds  of  the  Dwarka  Basin,  western  India.  Dilatilabrum  sp.  belongs  to  the  Family Dilatilabridae Bandel, 2007 and Conus (Lithoconus) gajensis Jain, 2014 belongs to the Family Conidae  Fleming,  1822) (1). 

The  existence  of  these  giant  gastropods  has  been  mentioned  by previous workers as a passing reference. Here we report two species with detailed morphological study on them which is lacking in literature. The temporal range of the genus Dilatilabrum was so far recorded from the Middle Eocene to the Early  Miocene (Aquitanian). With  this new find  of the giant Dilatilabriid gastropod range extends up to Middle Miocene. The spatio-temporal distribution pattern of the genus  Dilatilabrum indicates that after its origination during Middle Eocene, the genus was quite abundant and widespread in the Tethyan Region.

Due to a cooling event in the Tethyan Region, the genus compelled to migrate from west to east during the latest Oligocene and is seen to take refuge in the eastern Tethys. The situation prevailed during the Miocene, and with the closure of the Tethyan seaways the genus remained confined to the Indian subcontinent and eventually become extinct (Fig. 1). On the other hand, the giant conus i.e., Conus (Lithoconus) gajensis is the largest conus species (H is 233 mm, D is 150 mm) reported till now.

The species is found only confined to the Dwarka Basin and thus, is considered an endemic fauna to this western Indian basin (Fig. 2)

 

 

 

 

Conus (Lithoconus) gajensis (1)

Plate XXXIXfig. 1,2

mm. 147 x 132

Gaj Formation, Ranjitpur Member, Early Miocene

2,5 km. ESE of Ranjitpur (India)

Sp. No. 38/1234 Holotype, apertural and apical views respectively.

 

Conus gajensis (1)

 

 

 

Bibliografia

 

·        (1) - Kanishka Bose*, Shiladri S. Das*, Sandip Saha (2014) “Two giant gastropods from the Miocene of Dwarka Basin, Gujarat, India and their paleobiogeographic implications“

·        (2) - Jain (2014) "Neogene Fossils From Kathiawar, Gujarat, India With Special Emphasis on Taxonomic Description of Molluscs and Corals" (Courtesy of Kanishka Bose on 20/11/2023)