A preliminary review of the fossil species of Ranina Lamarck, 1801 (Decapoda, Brachyura, Raninidae), with systematic remarks
Author
Pasini, Giovanni
Author
Garassino, Alessandro
text
Natural History Sciences
2017
2017-04-10
4
1
43
72
http://dx.doi.org/10.4081/nhs.2017.310
journal article
10.4081/nhs.2017.310
2385-0922
12753805
?
Ranina berglundi
Squires & Demetrion, 1992
Fig. 2
Ranina berglundi
Squires & Demetrion, 1992: 43
, 44, figs. 128, 129.
Ranina berglundi
-
Schweitzer
et al.
2006: 24
, 27, 28, figs. 2.5, 2.6. –
Vega
et al.
2008: 54
, Pl. 1, figs. 13- 15, Pl. 2, figs. 1, 2. –
Schweitzer
et al.
2010: 74
. –
De Angeli & Beschin 2011: 13
. –
Van Bakel
et al.
2012: 208
. –
Karasawa
et al.
2014: 260
.
Type material
:
holotype
,
IGM
5913;
paratype
,
IGM
5914.
Type locality
: locality
CSUN
1220b;
Baja California Sur
(
Mexico
), Bateque Formation.
Geological age
: early Eocene.
Examined material
:
holotype
and
paratype
;
three specimens
(IHNFG-3013-3015) from the early Eocene (El Bosque Formation), locality El Veinte (
Chiapas
,
Mexico
), reported by
Vega
et al.
(2008)
;
one specimen
(
MHN-UABCS
/Ba7-3) from the middle Eocene (Bateque Formation), locality Waypoint 70 (
26°45.918’N
,
113°0.953’W
) (
Baja California Sur
,
Mexico
), reported by
Schweitzer
et al.
(2006)
.
Description by
Squires & Demetrion (1992)
: “
Moderate-sized raninid with ovate, moderately convex carapace, very broad in proportion to its length; widest along anterior one-fifth at outermost anterolateral spine area; carapace maximum width (including outermost anterolateral spines) equals total length; carapace width (excluding outermost anterolateral spines) 80 percent of total length; lateral borders curve inward, posterior margin very narrow; surface with small pits, sparse on anterior middle part, closer posteriorly and toward lateral and anterior borders; posterolaterally, pits in transverse rows of about 10; rostrum trifid, small, and pointed; fronto-orbital margin curved with three spines on each side; first (innermost) fronto-orbital spine small, outward-pointing, and separated from wider second spine by a short furrow; second fronto-orbital spine separated from forward-pointing and more prominent third spine by a very short and narrow furrow; length of fronto-orbital area about 60 percent of width of carapace (excluding outermost anterolateral spines); two anterolateral spines, equally spaced; first anterolateral spine forward-pointing, about equal in size to outermost fronto-orbital spine, but more pointed; second (outermost) anterolateral spine widest and strongest of all spines, extended at a 45-degree angle to a blunt point, with four serrations on anterior edge of spine (the middle two the strongest); posteriorly to second anterolateral spine, a fine raised rim extends around the carapace;
holotype
39 mm
in width (including outermost anterolateral spines),
38 mm
in length.
”
Discussion
. The type material described by
Squires & Demetrion (1992)
has trifid rostrum, first anterolateral spine single and second anterolateral spine, strongly directed outward, with four spinules on anterior edge.
Schweitzer
et al.
(2006)
assigned
six specimens
from the Bateque Formation (
Baja California Sur
) to this species, without adding additional information appreciably to the description of the carapace made by
Squires & Demetrion (1992)
. Later
Vega
et al.
(2008)
assigned tentatively
three specimens
from
Chiapas
(
Mexico
) to this species, pointing out, as difference from the type material, the first anterolateral spine bifid, small size, and distribution of the carapace dorsal pits. However, the review of the type material described by
Squires & Demetrion (1992)
allow us to establish that the first anterolateral spine is also bifid, well preserved in the left side of the
holotype
and slightly broken in the
paratype
, attesting that the specimens from
Baja California Sur
(
holotype
and
paratype
described by
Squires & Demetrion, 1992
) and
Chiapas
(
Schweitzer
et al.
, 2006
) could belong to the same species, though the smaller size of
Chiapas
specimens could be a diagnostic characters to distinguish these specimens from the type material (F.J. Vega pers. comm., 2016).
Fig. 2 -?
Ranina berglundi
Squires & Demetrion, 1992
. A) holotype, IGM 5913 (x 1.8). B) paratype, IGM 5914 (x 4.5).
Based upon the main morphological characters of
R. berglundi
, such as the trifid rostrum and the peculiar shape and arrangement of the anterolateral spines (above all the second one), we can attest that these characters do not fit those of
Ranina
, questioning the placement of
berglundi
within this genus.
Indeed
R. berglundi
from the early Eocene of Mexico and the rich sample of specimens from the late Oligocene (Rupelian) of the Ligure-Piemontese Basin (
NW
Italy
) ascribed to
R. speciosa
by
Allasinaz (1987)
have been assigned to a new genus within the Raninindae
sensu stricto
(
Pasini & Garassino, 2017
).