Pterygoplichthyini Armbruster 2004

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Pterygoplichthys
Photo by K.S. Cummings

Hemiancistrus annectens group
Photo by K.S. Cummings
TAXA LIST

The Pterygoplichthyini contains two genera, Pterygoplichthys and an undescribed genus referred to as the Hemiancistrus annectens group by Armbruster (1998). It should be noted that I misspelled Pterygoplichthyini as Pterygoplichthini in Armbruster (2004).  The two genera are supported as sisters by only one derived characteristic (a modified stomach that is attached to the abdominal wall by a net of connective tissue, see below); however, the Pterygoplichthys group shares with Ancistrini the derived presence of an evertible patch of plates on the cheek (see below).  No true difference exists in the ability of members of the Pterygoplichthys group to evert the cheek plates and the ability of members of Ancistrini.  The two genera differ most obviously in the number of dorsal fin rays (7 in the H. annectens group and 9+ in Pterygoplichthys).  The following information is an excerpt from Armbruster (2004).

Photo by J.W. Armbruster showing the evertible cheek plates and associated hypertrophied odontodes of Hemiancistrus aspidolepis of the H. annectens group.


DIAGNOSIS

The Pterygoplichthys group is diagnosed by one unique characteristic: the presence of an enlarged stomach that is attached to the dorsal abdominal wall by a connective tissue sheet (Armbruster, 1998c, below, photo by K.S. Cummings).


A = Artery
CTN = Connective tissue net
ES = Esophagus
INT = Intestine
PY = pylorus
S = Stomach
V = vein


COMPARISONS

Differs from the Rhinelepini and Hypostomus by having evertible cheek plates.  It is difficult to separate the species as a whole from Ancistrini as a whole except by examining the stomach for the presence of a connective tissue sheet (above).  Pterygoplichthys differs from all Ancistrini except Acanthicus and Chaetostoma by having more than seven dorsal-fin rays; from Chaetostoma by having plates on the abdomen; from the subgenus Acanthicus by having an adipose fin (vs. adipose fin absent) and by having the pterotic-supracleithrum taller than long (vs. longer than tall); and from the subgenera Leporacanthicus, Megalancistrus, and Pseudacanthicus by having more than ten teeth per jaw ramus.  The Hemiancistrus annectens group differs from Acanthicus and Chaetostoma by having seven dorsal fin rays (vs. 8+); from Ancistrus, Baryancistrus, Chaetostoma , Dekeyseria, Lasiancistrus, Acanthicus (Leporacanthicus), the Lithoxus group, Hemiancistrus megacephalus, Neblinichthys, Pseudancistrus, and Spectracanthicus by having plates on the abdomen (vs. abdomen naked); from Hypancistrus, Panaque, Parancistrus, and most Peckoltia by having the dentaries meet at an angle greater than 80° (vs. less than or equal to 80°); from all but Acanthicus, Dekeyseria, Chaetostoma platycephalus, Hemiancistrus landoni, Panaque, and Peckoltia by having keeled lateral plates (vs. unkeeled); and from Hemiancistrus landoni by having less than ten hypertrophied cheek odontodes (vs. 10+).


DISTRIBUTION

Known from nearly the entire range of loricariids except for the Guianas and coastal streams in southeastern Brazil.


LITERATURE CITED

Armbruster, J.W. 1998. Modifications of the digestive tract for holding air in loricariid and scoloplacid catfishes. Copeia 1998:663-675.

Armbruster, J. W. 2004. Phylogenetic relationships of the suckermouth armoured catfishes (Loricariidae) with emphasis on the Hypostominae and the Ancistrinae. Zoological Journal of the Linnean Society 141:1-80.
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