Description:
Body wider than its height at pectoral girdle area,
progressively compressed from pectoral to caudal peduncle,
ventrally flattened from pectoral girdle to anal origin.
Lateral line sloping ventrally on anterior one-third,
extending posteriorly to caudal peduncle, bending
abruptly onto dorsal lobe of caudal. Dorsal spine
relatively short and thick, shorter than pectoral
spine; anterior margin granulated on basal two-thirds,
with weak serrations on distal third; posterior margin
smooth on basal third, distal third with weak serrations.
Seven dorsal soft rays. Pectoral spine moderately
long and thick; two-thirds of anterior margin weakly
granulated, with weak serrations on distal third;
posterior margin straight on basal one-fourth, distal
three-fourths with weak serrations. Nine to eleven
pectoral soft rays. Posterior process of cleithrum
triangular smooth to rugose, slightly visible. Pelvic
fin deep and large at base, with six rays, and well-developed
fleshy protuberances in adult females. Adipose fin
low, with base moderately long, shorter than anal
base. Anal fin moderately high and long at base, with
16–19 rays and ventral profile convex. Caudal
peduncle moderately high. Caudal-fin forked, dorsal
and ventral lobes relatively long, dorsal lobe somewhat
longer than ventral lobe, slightly pointed.
Colouration in alcohol:Head
and body dark brown to bluish above, whitish below;
dorsal surfaces of pelvic proximally black, distally
lighter; anal dark, distal tips lighter; caudal grayish
to blackish. Sexual Dimorphism: Only
females have well-developed fleshy protuberances or
pads in basal portion of pelvics, especially during
reproductive season. Vomerine tooth patches and accessory
tooth patches not observed directly, but possibly
showing same variation described for A. canteri
and A. jimenezi. Etymology:
The specific name assimilis: Latin for similar,
described as “closely allied” to Hexanematichthys
hymenorrhinos (=Sciades
herzbergii) and A.
seemanni.
North
America: Pacific coast and coastal rivers
of North and Central America, from Gulf of California,
Mexico to Honduras. Type locality:
Estuary at Mazatlán, Sinaloa, W. Mexico.
If you would like to contribute to the monthly
factsheets with an article, information or photos, please e-mail
me. You will of course be credited for your work.
If you would like to donate any denomination
of monies to the site just click the above link button. All proceeds
will go to running the site and hopefully to keep it going for a few
years yet.