Bassipterus is almost completely known, with the first to fifth pair of limbs and type B genital appendage being the only unknown body parts.
The body had a lanceolate (lance-shaped) and streamlined shape.
The prosoma ("head") was long, rounded and tray-shaped.
The carapace (dorsal plate of the head) was surrounded by a narrow marginal rim, with eyes placed frontally, placed intramarginally (within the margin) and unusually long.
PE 6139, a 15.2 millimeter (0.6 inch) long carapace, had eyes 4.5 mm (2 in) long and 2.2 mm (0.1 in) wide.
The ocelli are preserved, and were placed in the center of the carapace, immediately behind the eyes.
The metastoma (a large plate part of the abdomen) was long, truncated (shortened as by cutting it) at the base and cordate (heart-shaped) in the anterior (frontal) part.
One specimen preserves a metastoma of 8.3 mm (0.3 in) in length and 5 mm (0.2 in) in width.
Of the appendages (limbs), the swimming legs (sixth pair of appendages) are the only known ones.
These were of Hughmilleria-type (with enlarged seventh and eighth leg segments and the ninth very small), but in this species, it was serrated along the anterior edge of the sixth to seventh joints.
The terminal joint was a sharped spur.
The mesosoma (comprising body segments 1 to 6) was tapered, with the first tergite (dorsal part of the segment) considerably narrower than the rest.
The metasoma (comprising segments 7 to 12) followed the taperation of the mesosoma and ended in a long dirk-like telson ("tail").
The telson was smooth in the ventral part, but carinated (with a keel) dorsally towards the end, which was a very sharped point.
The specimen PE 6208 had a 32.5 mm (1.3 in) long telson.
The ornamentation in Bassipterus is well known and developed.
The carapace was covered by triangular scales.
The tergites and abdominal plates had mucrones (sharped points) typical of Adelophthalmidae, but these were considerably larger and more prominent than in related genera.
In some places, the mucrones touched each other and formed a rhombic ornamentation, while in others, they were so elongated that they resembled the linear striations present in the more derived ("advanced") genus Adelophthalmus.

The morphology of the genital operculum (a plate-like segment which contains the genital aperture) allows an easy differentiation between Bassipterus and the other adelophthtalmids.
The type A genital appendage (assumed to represent females) was long, reaching the second pair of abdominal plates, and was divided into three joints.
The first had a short, triangular and hastate (with protruding lobes) portion followed by a tubular shaft that ended in two lateral triangular projections at the point of union with the following joint.
The second joint was shorter and composed of three different areas.
On both sides of the central shaft, two long narrow sclerites (hardened parts), possibly plates, lengthened themselves at their ends.
The third joint was very short and finished in two long points reminiscent of Eurypterus, a more basal genus.
The appendage in its entirety was covered by triangular mucrones which pointed outwards.
The genital operculum differentiates Bassipterus from other eurypterid genera and suggests a close relationship with Pittsfordipterus.
Bassipterus is almost completely known, with the first to fifth pair of limbs and type B genital appendage being the only unknown body parts. The body had a lanceolate (lance-shaped) and streamlined shape. The prosoma ("head") was long, rounded and tray-shaped. The carapace (dorsal plate of the head) was surrounded by a narrow marginal rim, with eyes placed frontally, placed intramarginally (within the margin) and unusually long. PE 6139, a 15.2 millimeter (0.6 inch) long carapace, had eyes 4.5 mm (2 in) long and 2.2 mm (0.1 in) wide. The ocelli are preserved, and were placed in the center of the carapace, immediately behind the eyes. The metastoma (a large plate part of the abdomen) was long, truncated (shortened as by cutting it) at the base and cordate (heart-shaped) in the anterior (frontal) part. One specimen preserves a metastoma of 8.3 mm (0.3 in) in length and 5 mm (0.2 in) in width. Of the appendages (limbs), the swimming legs (sixth pair of appendages) are the only known ones. These were of Hughmilleria-type (with enlarged seventh and eighth leg segments and the ninth very small), but in this species, it was serrated along the anterior edge of the sixth to seventh joints. The terminal joint was a sharped spur. The mesosoma (comprising body segments 1 to 6) was tapered, with the first tergite (dorsal part of the segment) considerably narrower than the rest. The metasoma (comprising segments 7 to 12) followed the taperation of the mesosoma and ended in a long dirk-like telson ("tail"). The telson was smooth in the ventral part, but carinated (with a keel) dorsally towards the end, which was a very sharped point. The specimen PE 6208 had a 32.5 mm (1.3 in) long telson. The ornamentation in Bassipterus is well known and developed. The carapace was covered by triangular scales. The tergites and abdominal plates had mucrones (sharped points) typical of Adelophthalmidae, but these were considerably larger and more prominent than in related genera. In some places, the mucrones touched each other and formed a rhombic ornamentation, while in others, they were so elongated that they resembled the linear striations present in the more derived ("advanced") genus Adelophthalmus.
The morphology of the genital operculum (a plate-like segment which contains the genital aperture) allows an easy differentiation between Bassipterus and the other adelophthtalmids. The type A genital appendage (assumed to represent females) was long, reaching the second pair of abdominal plates, and was divided into three joints. The first had a short, triangular and hastate (with protruding lobes) portion followed by a tubular shaft that ended in two lateral triangular projections at the point of union with the following joint. The second joint was shorter and composed of three different areas. On both sides of the central shaft, two long narrow sclerites (hardened parts), possibly plates, lengthened themselves at their ends. The third joint was very short and finished in two long points reminiscent of Eurypterus, a more basal genus. The appendage in its entirety was covered by triangular mucrones which pointed outwards. The genital operculum differentiates Bassipterus from other eurypterid genera and suggests a close relationship with Pittsfordipterus.
Bassipterus