Glypturus panamacanalensis, Klompmaker & Hy̆z & & Kowalew, 2016

Klompmaker, A., Hy ̆ z, Matu ̆ s, , Roger W. Port & Kowalew, nd Michał, 2016, Growth, inter- and intraspecific variation, palaeobiogeography, taphonomy and systematics of the Cenozoic ghost shrimp Glypturus, Journal of Systematic Palaeontology 14 (2), pp. 99-126 : 110-112

Glypturus panamacanalensis sp. nov.

( Figs 12, 13)

Diagnosis. Lateral tuberculation on outer propodal side from base of fixed finger diagonally to lower margin and proximal lower corner. Lateral tuberculation on inner propodal side covering large lower part of manus in medium to large specimens with lower margin of tuberculated area diagonally crossing from area of articulation of dactylus toward (but not reaching) proximal lower corner, tuberculation in small specimen more variable but mostly as in larger specimens. Occlusal margin of dactylus with two elongated, strong teeth exhibiting smooth top. Outer side carpus with tubercles near lower margin; inner side with tubercles on lower ~75%.

Derivation of name. Derived from the location where the type specimens were found: at beaches near the entrance of the Panama Canal near Panama City, Panama. The name also acknowledges the tremendous efforts in constructing, maintaining, and expanding the Panama Canal .

Material. Holotype: UF 248033 ( Fig. 12F — H) . Paratypes: UF 126585 ( Fig. 12A, B), 248035 ( Fig. 12C — E), 248032 ( Fig. 12I — L), 126719 ( Fig. 12Q, R), 246099 ( Fig. 12S — U) and 246078 ( Fig. 12Y).

Other material (P = propodus; D = dactylus; C = carpus; M = merus; FF = fixed finger): UF 246095 ( Fig. 12M, N), 248030 ( Fig. 12O, P), 246097 ( Fig. 12V — X), 131471 ( Fig. 12Z, Al), 248008 ( Fig. 12 Bl, Cl), 124236 (1P1C), 126571 (8D), 126572 (1D), 126573 (2P), 126574 (3P), 126575 (1D), 126576 (1FF), 126577 (2P), 126578 (13P), 126581 (1P), 126582 (2P), 126583 (1C), 126584 (2C), 126594 (5P), 126595 (8P), 126645 — 126646 (23P each), 126647 (16P), 126648 (28P), 126649 (23P), 126650 (24P), 126651 (19P), 126652 (20P), 126653 (13P), 126654 — 126655 (4FF each), 126663 (15P), 126664 (13P), 126665 (2FF), 126685 — 126686 (18P each), 126687 (11P), 126688 (20P), 126689 (21P), 126717 (4P), 126718 (1P), 126739 (3FF), 126740 (1FF), 126741 (12P), 126742 (2P), 230782 (1P), 230816 — 230841 (1P each), 246064 (2P), 246065 — 246070 (1P each), 246072 — 246076 (1P each), 246077 (1FF), 246079 (2P), 246080 — 246086 (1P each), 246087 (1C), 246088 — 246090 (1P each), 246091 (2P), 246092 (1P), 246093 — 246094 (1FF each), 246096 (1C), 246098 (1C), 246100 — 246101 (1C each), 248050 — 248053 (1P each), 248936 — 248937 (1P each), 250088 (2P), 251703 — 251725 (1P each), 251802 — 251803 (3P each), 251804 (1P), 251805 — 251807 (2P each), 251830 — 251833 (1P each), 251834 (7P), 251835 (4P), 251836 — 251839 (1P each), 251840 (2P), 251841 (3P), 251842 — 251843 (1P each) and 251844 (4P).

Occurrence. Collected (ex situ) on Amador and Farfan beaches (type locality) at the entrance of the Panama Canal near Panama City, Panama. The age is Holo-Pleistocene (see Geological setting); the formation is unknown. Additionally , the species is known from the middle Pleistocene Bermont Formation of Florida (Belle Glade 01 locality) and the upper Pleistocene Jaimanitas Formation of Cuba (Good Road 01 locality).

Description. Manus up to ~ 25 mm long and ~ 20 mm tall, length/height ratio ~1.0 — 1.3. Upper margin curving inward distally, proximally keeled, typically bearing three prominent spines pointing distally, proximalmost spine around mid-margin, keel terminating in blunt corner proximally. Lower margin sharp and keeled, lined with a row of setal pits on inner lateral side. Proximal margin convex on outer face, concave on inner; heightwise groove near proximal margin concave on inner side, concave to straight on outer side. Distal margin with protrusion just above fixed finger, hinge point with dactylus expressed as notch. Lateral tuberculation on outer side from base of fixed finger diagonally to lower margin and proximal lower corner. Lateral tuberculation on inner side covering large lower part of manus in medium to large specimens with lower margin of tuberculated area diagonally crossing from area of articulation of dactylus toward (but not reaching) proximal lower corner, tuberculation in small specimens more variable but mostly as in larger specimens. Fixed finger curving inward, triangular, sharply pointed, with distinct blunt tooth on occlusal margin around mid-length, tooth pointing distally. Dactylus stout; occlusal margin with two elongated, strong teeth exhibiting smooth top; tip hooked, curving downward. Carpus trapezoid, slightly taller than long; upper margin keeled and smooth with setal pits on inner part margin; lower margin keeled, shows bases of spines on inner side; distal margin straight to slightly concave; proximal margin concave on inner side, convex on outer side; outer side with tubercles near lower margin only; inner side with tubercles on lower ~75%. Outer side merus with longitudinal keel in centre, tuberculated below keel, spinose and convex lower margin. Other parts of species not preserved.

Remarks. Intraspecific variation is observed in the strength of the teeth on the dactylus ( Fig. 12A, B, M — R) and the tooth on the fixed finger (compare Fig. 12C to 12F, I). Furthermore, the number of spines on the upper margin of the propodus is typically three, but some (<10%) specimens exhibit two ( UF 248053) or four spines ( UF 248050 — 248052). Size-related variation is particularly expressed in the tuberculation pattern on the inner side of small specimens as opposed to the more stable coverage in larger specimens, an increasing length/height ratio with size, and an increasing coverage of tubercles on the inner side with size. Although a higher number of major propodi (defined here: length manus ± 15 mm) are right-handed (193 versus 159 left-handed), this is not statistically significant (x 2 = 3.28; p = 0.07).

Glypturus panamacanalensis sp. nov. differs from G. acanthochirus , G. armatus , G. laurae , G. persicus , G. munieri and G. pugnax in that the tubercles cover a substantially greater area on the outer side of the propodus. Similarly, the inner side of the propodus of G. panamacanalensis sp. nov. has a greater coverage of tubercles compared to G. acanthochirus , G. armatus and G. laurae . Conversely, tubercular coverage on the inner side of G. fraasi is greater than in G. panamacanalensis sp. nov. The tubercles on the outer side of G. berryi reach above the lower proximal corner, which is not the case in G. panamacanalensis sp. nov. Glypturus spinosus bears much stronger spines on the upper margin compared to the new species, although spines may be variable (see Hy̆zńy & Muller 2012, p. 982). Tubercular patterns are more difficult to use to distinguish G. toulai and G. sikesi sp. nov. from the new species, but sufficient differences were found to erect G. panamacanalensis sp. nov. (see above).

One specimen ( UF 126570) exhibits a swelling in the fixed finger ( Fig. 13A — D). Isopod-induced swellings are known to occur in the branchial region of the carapace of decapod crustaceans including shrimp (Frantescu ¸2014; Klompmaker et al. 2014), but not in the fixed finger. These ichnofossils were named Kanthyloma crusta Klompmaker et al., 2014 . The origin of this particular swelling is unclear, but it may represent an example of a bacterial infection (Christopher Boyko, pers. comm. 11 February 2013). Another specimen ( UF 246071) shows a concavity on the upper margin of the propodus accompanied by a subcircular indent on the inner side of the margin and a concave ridge on the outer side ( Fig. 13E — G). The keel on the upper margin is somewhat offset. There are no signs of a fracture. It is speculated here that this could be a failed predation attempt or an attack by a conspecific individual (antagonistic behaviour), perhaps directly after the moulting phase when the cuticle was not fully hardened, which may explain why no fracture is observed. Antagonistic behaviour is known from modern ghost shrimps (e.g. Nihonotrypaea Manning & Tamaki, 1998 ), whereby the major cheliped is protruded and used to grapple with the chelipeds of another individual ( Shimoda et al. 2005). Predators of fossil decapods are numerous (e.g. Klompmaker et al. 2013, table 1); those of modern ghost shrimp include fish, crabs, birds and juvenile grey whales (e.g. Posey 1986; Dworschak et al. 2012).