Shane's World Right Arrow Species Right Arrow A Guide to the Identification of Plecos • Article © Sandor Tüllmann, uploaded April 18, 2009

Introduction
This guideline is intended to support the hobbyist in determining the identification of their loricariid catfish at least down to genus level. Of course, for this purpose, no exact, meristic values are available and are therefore not used as distinguishing characteristics in this context, rather, and only in some cases, relative differences to other closely related genera can be given in order to allow for identification. Thus, characteristics are presented that allow identification solely based on visible differences, discernible with live individuals. These differences are, in general, only apparent with adult or semi-adult fish. Certainly, this compilation does not claim to provide scientifically accurate descriptions or determinations. In this context it should be stressed that the author is critical towards some recently published points of view in the scientific community and recognizes some genera as valid that are currently treated as synonyms by leading scientists. Where necessary, alternative group descriptions are given, consistent with current research. It goes without saying that the opinions expressed here are solely those of the author. Differentiating characteristics are based on observations of the author or, where not available, on conclusions drawn from scientific literature. Of course, these characteristics do not claim to be exhaustive.

For the sake of simplicity, contrary to common use, 'loricariid catfish' is meant to represent members of the subfamily Hypostominae, in distinction to Hypoptopomatinae and Loricariinae. Also, Neoplecostominae will not be covered in this contribution.

Finally, some words regarding a rather morphological topic seem appropriate. Contrary to the still widely accepted common sense, loricariid catfish do not possess a bone called the interoperculum. Connected to this, it is important to note that the widely known and famous 'interopercular odontodes' cannot exist in loricariid catfish due to lack of this very bone. Indeed, this is based on a misidentification by some early scientists who wrongly identified a cheek bone as the interoperculum. Still, in some genera, odontodes are found on some of the bones belonging to the gills (as would be the interoperculum, would it exist). Therefore, the correct term for this spiny growth would be 'cheek- and gill-odontodes'. In order to prevent misconceptions due to the growth of odontodes on the cheeks (not to be mixed up with odontodal growth on the cheek bone!) present in some genera, in the following, the term 'gill odontodes' or variations thereof will be used. Interopercular odontodes will not appear, however.

The Acanthicus group
This group contains, with a few exceptions, only large loricariids, that tend to grow to sizes of 50-100 cm TL. Such a size can already serve as a first hint to membership of this group. Hallmark property of all members is a comparatively slender and elongated body. The head is usually longer and more slender in proportion as compared to other genera. If additionally some gill odontodes are found (those do not have to be as obvious and permanently visible as in Hypancistrus or Peckoltia), one can be quite sure to be facing a member of this group.
With the exception of Leporacanthicus, all members of this group possess a large number of long and strong odontodes covering the whole body, which certainly can pose a threat for the keeper.

With this information at hand, members of the genus Leporacanthicus are easily distinguished by their long head, strongly reduced dentition (these catfishes are carnivorous) and the only slightly developed odontodal growth on the body (as compared to other members of the group; within the loricariid catfishes, this growth still is significant) from other genera in- and outside the Acanthicusgroup. Within the group, a special emphasis can be made on dentition, since members of the genus Leporacanthicus are the only ones in the group that have markedly longer and fewer teeth in the upper jaws than in the lower ones. Finally, these animals have fimbriae at the upper part of the mouth disk.
This genus comparatively contains the smallest members of the group (none of them gets bigger than approx. 30 cm TL) and has no real giants.

Telling a member of Megalancistrus from the other group members is easy. They show comparatively the most massive head with concomitant heavy growth of odontodes covering the body. Final certainty can be obtained by counting the soft rays in the dorsal fin. Owing to the unusual number of 10 soft rays and in conjunction with the evertible gill odontodes, this genus can be differentiated from any other known genus of loricariid catfish. All known species of this genus can reach total lengths of 80 cm and beyond.

While commonly termed 'elven catfish' (Elfenwels) in some parts of the world, especially adult members of the genus Acanthicus show little of the elegance and subtlety any fan of fantasy literature immediately links with Elves. This common name stems from the elegant body shape of young individuals imported by the thousands from South America. Few people buying them are aware of the fact that they will inevitably grow to rather territorial and wayward creatures which have (to stay in fantasy) more in common with Orcs than Elves. Additionally, according to present knowledge, all members of this genus reach total lengths of 100 cm and more! Identification of a member of this genus is relatively straight forward. The most prominent feature of typical body shape of an Acanthicus is the lack of the adipose fin. Also, the bone plates at the back end of the head are decisive, as they are merged to three rather robust plates, immediately discernible in larger specimens. With large fish, one might tend to abandon the term odontodes for the spines at the back end of the body, since they more closely resemble blades or sickles (a centimeter long!). Finally, among the members of this group, Acanthicus show the least reduced dentition. Fortuitously, in larger specimen, the number of teeth can be easily counted without magnification at the front glass of the tank.

The catfishes of the genus Pseudacanthicus are not termed 'cactus catfish' by chance. They show heavy growth of strong odontodes covering the whole body, most prominent at the back end. The distinction from other members of the group is a little tricky, although anyone who ever saw a live Pseudacanthicus, can immediately spot them. Since from the scientific point of view, the most pronounced differences are found in the bone structure, the hobbyist must refer to some relative differences in the members of this group.

Compared to Acanthicus, the Pseudacanthicus show a rather reduced dentition, a sign of their carnivorous feeding habits. While they share this reduced dentition with Leporacanthicus, Pseudacanthicus can be easily distinguished from them through the different teeth shape in the lower jaw as well as the heaviness of the odontodal growth. For differentiation with respect to Megalancistrus, one can again resort to dentition, which is less reduced in Megalancistrus. Additionally, the head shape in Megalancistrus appears to be considerably more heavy and bulky. Finally, the number of soft rays in the dorsal fin can be applied for identification, since Pseudacanthicus possess eight (seldom nine) soft rays, while Megalancistrus, as stated above, usually have ten.

The maximum length in Pseudacanthicus is rather heterogeneous, with a maximum of approximately 20 cm in Pseudacanthicus sp. 'L 65' up to 100 cm TL for Pseudacanthicus histrix and its close relatives.

All members of the Acanthicus group require comparatively large aquaria, first due to their sheer size, but second due to the rather territorial behaviour in adult fish.

The Ancistrus-Group
The genera summarized in this group are, as are the members of the preceding group, part of the Tribe Ancistrini. A common characteristic of this tribe is the presence of evertible gill odontodes. All members of this group additionally show a unique trait: with all genera in this group (albeit occasionally only discernible during spawning season), the animals show outgrowth on the head, be it fleshy tentacles or hard odontodes. Females may also show this growth, however, it usually is considerably less developed than in males. Additionally, this is dependent on the respective genus. Although there are some species reaching total lengths of 30 cm TL, this group consists of small to medium species, that only occasionally grow to more than 15 cm TL.

Here, the genus Ancistrus is easiest to identify, provided, (at least) one adult, male specimen is present. Ancistrus are the only known species of catfish in which the males develop fleshy, antenna-like outgrowth on the head. Within most species, the females also develop some tentacles, however, this is usually considerably less developed. Additionally, in general only male develop tentacles on top of the snout, more precisely on the connecting line between the eyes and the tip of the snout. Contrary to almost all other loricariid catfish, the rim of the snout in Ancistrus is naked, which can be easily felt. Usually, the gill odontodes are not numerous, but rather thick and bent forward, such that they easily get stuck in nets. In relaxed position, these odontodes are mostly not immediately apparent.

While identification down to genus level is easy for Ancistrus, the differentiation at species level is far more difficult, and mostly doomed to failure without knowledge of the precise capture locality.

The genus Guyanancistrus (according to present scientific status, the Pseudancistrus brevispinis - group) is not easily identified. The hobbyist is faced with a genus that is comparatively flattened, as most members of the Ancistrusgroup. The body is almost free of odontodes, adult males, however, show an impressive set of odontodes on the first pectoral fin rays. Additionally, the rim of the snout is covered with numerous short odontodes, that are not apparent at first sight. In contrast to most loricariid catfish, the tip of the snout is naked, while the outer rim of the snout is, in contrast to Ancistrus, covered with plates.

While most members of the Ancistrusgroup possess few, but thick gill odontodes, Guyanancistrus show a large number of rather thin, but very long gill odontodes, that often extend down to the insertion of the pectoral fins. The dentition is quite numerous and, as with all genera in this group, the jaws are arranged almost parallel, as is typical for surface scrapers feeding mainly on aufwuchs.

Hopliancistrus show, comparable to the just mentioned Guyanancistrus, a plethora of thin (but, in comparison, stronger developed) odontodes on the rim of the snout. Also with respect to other morphological characteristics, Hopliancistrus and Guyanancistrus are quite similar. They are, however, easily distinguishable based on the gill odontodes: While Guyanancistrus show numerous long odontodes, in Hopliancistrus, one finds extremely few (usually, a maximum of three), but very thick and strongly bent odontodes. Usually, they are not immediately apparent in relaxed position.

Considerably stronger odontodal growth along the rim of the snout is found in Delturus. The odontodal growth in this genus is intermediate between Hoplicanistrus and Lasiancistrus (see below), but the genus is easily identified based on the (with respect to this group) uniquely large head with its rather large sucker mouth. Also, the dorsal fin ray count is unique within this group, amounting to 8-10 branched rays (usually, 7 soft rays are found). Finally, Delturus do not possess evertible gill odontodes, which makes them members of the Tribe Hypostomini rather than Ancistrini. Identification should thus be unambiguously possible and easy.

Lasiancistrus can be regarded as the logical extension of Guyanancistrus and Hopliancistrus with respect to the development of odontodes along the rim of the snout. Especially large, adult males can develop comparatively numerous long, but thin odontodes, which are most apparent in the cheek area. Males in spawning condition also develop elongated pectoral fins. As in Guyanancistrus, the gill odontodes are numerous and long and can be extended fan-like for defence. While adult specimen are easiest identified based on their unique combination of odontodal growth, juveniles show a different, very distinctive trait: the strongly emarginate caudal fin is only pigmented in the low lobe, such that at first sight, they appear as if the upper lobe had been cut off.

A unique form of odontodal growth is found in the genus Neblinichthys. Here, males develop extremely long, forward pointing (!) odontodes on top of the snout, that extend beyond the tip of the snout. Unfortunately, members of this genus have not been imported yet (at least not into Germany) but if they ever will, they probably won't be backed in the usual plastic bags..

For Dekeyseria, it is difficult to identify simple, descriptive characteristics. They are comparatively slender catfish, that additionally appear to be quite flat. As compared to other loricariid catfish showing such a body shape, the head is long and strongly elliptic, almost blunt. These traits can be used to distinguish Dekeyseria from other catfish with rather long heads, which usually show a pointed head shape. The bone plates at the sides are strongly keeled, which can, in conjunction with the gill odontodes, the, especially in males, strongly developed growth of odontodes on the first pectoral fin ray (which is additionally often coloured reddish) and the typical aufwuchs-eater dentition, be used for identification of members of this genus. At least during spawning season, males develop some short odontodes along the rim of the snout. If one is dealing with an 'attractively' coloured catfish, however, it is most probably not a member of Dekeyseria, since they are usually grey-brown in colour.

Based on morphology, the genus Zonancistrus strongly resembles Dekeyseria (and is therefore at present regarded as the Dekeyseria brachyura group). Zonancistrus, however, appear to be much less elongated as compared to Dekeyseria, especially the tail appears to be much shorter on relative terms than in Dekeyseria. Also the foremost part of the body is broader in appearance, as is the head and is extremely flat. Zonancistrus can be coloured brightly yellow-black. This is, however, dependent on condition and mood, such that the fish can become almost grey if kept in inappropriate conditions.

Just like Zonancistrus, Pseudolithoxus are extremely flattened catfish, which do not appear as broad as Zonancistrus, but strongly resemble their body shape otherwise. The pectoral fins of Pseudolithoxus can be used for identification. They show extremely long odontodes (especially with males), as compared to other members of the group. Also, the pectoral fins are very long, sometimes reaching back beyond the anus! Through the combination of odontodal growth, flattened body and the long pectoral fins, Pseudolithoxus can be identified beyond any doubt.

Lithoxus and Exastilithoxus
The comparatively tiny members of these genera are easily identified. Both genera contain extremely flat catfish, a trait that, in conjunction with the large suckermouth, hints at the strong currents found in their habitats. Both genera are presently unique in having fimbriae around their whole disc shaped sucking mouth. While in Exastilithoxus these fimbriae are quite long and immediately apparent, they are more like jags in Lithoxus. This trait is at least at present unique within the loricariid catfish, such that these genera are readily identified. In both genera, especially the males develop extremely long odontodes on the first ray of the pectoral fins, that appear like combs.

Lithoxancistrus (the Pseudancistrus orinoco group) does not really fit into any group defined here, even though some resemblances can be found with the Ancistrusgroup. The most important differences with this group are, however, not visible in live specimen. At first sight, they most strongly resemble Lasiancistrus, since Lithoxancistrus also develop considerable odontodal growth in males, this growth being stronger developed than in Lasiancistrus. Constraining the identification to easily apparent differences, the unique colouration of the caudal fin present in Lasiancistrus is not found in Lithoxancistrus. Additionally, Lithoxancistrus is considerably more flattened.

Additionally, the genus Pseudancistrus is quite similar, but can be easiest differentiated from Lithoxancistrus by the gill odontodes. While Lithoxancistrus presents readily visible, evertible odontodes, they are almost invisible in living specimen of Pseudancistrus. The odontodal growth at the rim of the snout is, on the other hand, much stronger developed in Pseudancistrus, even stronger than in Lithoxancistrus. If one is faced with a collection of adult specimen, these odontodes should immediately give away the genus.

Chaetostoma and 'Relatives'
The Chaetostomagroup might also be termed the 'thick-lipped'group, although it is more the rim of the snout that the lips that are thickened. All genera assembled in this group generally stem from strongly flowing habitats such that the representative characteristics of this group can be regarded as adaptations to this specific type of habitat.

Eponymous for this group is the genus Chaetostoma, which, among those assembled in this group, is the one most widely known in the hobby. They are typically rather flat catfish, equipped with an oversized sucking disk. Their suckermouth disks are as wide as is the head, which, taken by itself, already appears to be disproportionately wide. Just like Ancistrus, the rim of the snout of Chaetostoma is not covered with plates and usually noticeably thickened. The gill odontodes are hardly discernible and only weakly developed.

Cordylancistrus show, as do Chaetostoma, wide heads, but in direct comparison, do not appear as flattened as Chaetostoma. The thickened 'lip' is also readily visible, however, in contrast to Chaetostoma, the rim of the snout is completely covered with plates, such that the distinction of these two genera should be straight forward.

For differentiation of Dolichancistrus with respect to Chaetostoma, the gill odontodes can be employed. While Chaetostoma only shows weakly developed gill odontodes, these are more strongly developed in Dolichancistrus. Especially apparent is usually a single odontode, that extends far beyond the rest of the odontodes. Additionally, the rim of the snout is covered with bone plates, as is found in Cordylancistrus. In contrast to them, however, the rim of the snout is covered with a set of small odontodes, as is found in Hopliancistrus or Lasiancistrus.

Strong resemblance with Dolichancistrus is found in Leptoancistrus, as all characteristics just mentioned for Dolichancistrus also apply for Leptoancistrus. The distinction is, nevertheless, straight forward, since Leptoancistrus is lacking the adipose fin as well as the anal fin. Therefore, if Leptoancistrus show up in the hobby at some time, they will be easily identified.

The Hemiancistrusgroup
Within this group, by far the most frequently kept catfish are present. At the same time, this group poses the most problems from the scientific viewpoint, since a lot of the genera present are not well defined. Ironically, the practicing hobbyist has less problems in identifying members of the genera of the Hemiancistrus-group, since in the hobby, identification based on 'feeling' or 'general impression' is possible and usually the only possible way, if one does not wish to dissect his fosterlings. Scientists, on the other hand, have to rely on differences in measurable data which is more difficult to come up with in this group. All members of this group possess readily visible, evertible gill odontodes.

The easiest to identify in this group are Baryancistrus, which belong to the most beautiful, but regrettably also to the most demanding loricariid catfish. Baryancistrus are easily recognized by their bulky head, which is not only comparatively wide, but also rather high. The mouth with its myriad of small teeth identifies Baryancistrus as highly specialized aufwuchs or biofilm feeders. Well suited for identification is a skin membrane which links the dorsal fin to the body plates between dorsal and adipose fin. This membrane is only visible with strongly erect dorsal fin. Such a membrane is otherwise only found in the Parancistrusgroup and 'Baryancistrus' demantoides, where the latter is presently regarded as Baryancistrus, while the author is convinced that it is to be placed in its own genus, since the membrane is the only commonality of 'Baryancistrus' demantoides and Baryancistrus. Parancistrus will be treated below, for now it suffices to state that said membrane does not extend to the adipose fin in Baryancistrus, while it does so in Parancistrus.

Probably every ichthyologist involved in catfish has a different notion of what a Hemiancistrus is. Therefore, this is (together with Hypostomus) the only genus for which no general characteristics can be given if one does not want to cover half of the other genera with these characteristics, as well. Here, a considerable amount of scientific work is still needed, and also the hobbyist will have problems to unequivocally identify a Hemiancistrus, since, as mentioned, depending on the primary literature applied, Hemiancistrus might show completely different characteristics. The only meaningful approach here is to cut 'the' Hemiancistrus strongly down to the type species (Hemiancistrus medians). If this is done, a surprisingly small group of catfish remains that can be regarded as Hemiancistrus sensu stricto. Ironically, this group has yet to play its part in the hobby. The body shape of the Hemiancistrus sensu stricto resembles that of Baryancistrus with their rather massive head shape. A membrane at the dorsal fin is just barely indicated, but far less developed as in Baryancistrus. Therefore, a distinction should be easily made. It will become problematic, however, if one intends to discuss Hemiancistrus, because firstly one would have to argue about just what Hemiancistrus is supposed to mean for the sake of that discussion.

Among the most widely known genera of loricariid catfish, the members of the genus Hypancistrus are found. This rather young genus is easily identified based on a number of characteristics, identification down to species level is, however, usually not as straight forward and in most cases completely hopeless considering the vast number of different species, types and variants found in black/white Hypancistrus, for instance. As is often the case, any person that came across a Hypancistrus species more than once can immediately spot one without much thinking. The species of this genus are generally more flat than Peculiar and 'well proportioned', meaning, that no part of the body appears to be considerably enlarged or extraordinarily shaped. The most certain way to identify Hypancistrus is by the shape of their teeth, as they are unique within loricariid catfish: while the comparatively strong reduction of dentition hints to a carnivorous feeding style, the genus is identified by the teeth in the lower jaws being considerably longer than those in the upper jaws.

Although the genus Peckoltia still poses some problems on scientific terms, it is, with a few exceptions, easily identified in the hobby. The species of the genus appear to be rather compact and a little stocky as compared to similar genera like Hypancistrus. They are considerably smaller than the otherwise most similar Baryancistrus or Ancistomus (see below). The most certain way to identify a Peckoltia is by its dentition if one does not want to reside to intuition, which usually works very well with Peckoltia. Unlike Hypancistrus, the teeth of Peckoltia are of the same length in upper and lower jaw, while the number of teeth is, if compared to similar genera, slightly reduced. Also, the lower jaws are almost arranged rectangular with respect to each other, i. e., almost form a 90° angle, while typical aufwuchs/biofilm feeders have the upper jaws arranged with an angle of almost 180°. This suggests that Peckoltia are omnivorous. A little off is the well-known species Peckoltia sp.'L 134', which according to the authors opinion represents a species intermediate between Hypancistrus and Peckoltia, but does not really fit into any of these genera.

Easy to recognize are Peckoltichthys (better known especially in Europe under the Synonym Sophiancistrus; also appears as Peckoltia ucayalensis). This genus is identifiable by the shape of the forehead, that rises in a straight line from tip of snout to insertion of the dorsal fin. Together with the eyes being low on the side of the head, this genus resembles species of the genus Hypoptopoma more than any of its closer relatives within the loricariid catfish.

Ancistomus (also known as the Peckoltia snethlegae -group; some also regarded as Hemiancistrus) is hard to tell from Peckoltia based on measured data, which is probably one of the reasons why this genus is not readily accepted within the scientific community. Provided the hobbyist is dealing with adult specimen, the distinction is rather straight forward, however. Ancistomus generally grow considerably larger than Peckoltia: while Peckoltia do not grow beyond 15 cm TL, the smallest members of Ancistomus already grow beyond this size. On the other hand, they also do not become true giants, usually, the hobbyist has to expect about 20-25 cm TL from Ancistomus. As compared to Peckoltia, they appear to be more elongated and not as stocky. They have slightly more teeth than Peckoltia and, most importantly, the lower jaws form a considerably wider angle than is found in Peckoltia.

Panaque and Panaqolus
These two genera are distinguished from other loricariid catfish by their special type of feeding, which they only share with Cochliodon, as they are mainly wood eaters. While Cochliodon as a member of the Tribe Hypostomini does not have any evertible gill odontodes, these are almost always visible in Panaque and Panaqolus and can reach impressive lengths.

Both genera are easily identified based on their dentition, as it is strongly reduced and spoon shaped (which is, however, only visible with magnifying glasses in small specimen), and the jaws are arranged in acute angles.

Panaque are identified by their unique head shape. They show extremely elongate heads, where the forehead steadily rises to the dorsal fin in an acute angle. The eyes are comparatively far at the back end of the skull. This creates a uniquely long snout that makes Panaque unmistakable. Also, they grow to considerable sizes with small species reaching 30 - 40 cm TL, provided, they are granted the space to grow.

A similar head shape is found in Panaqolus (Panaque dentexgroup or 'dwarf Panaque'; according to the authors opinion, closely related to Peckoltia and/or Hypancistrus, but only distantly to Panaque). This trait is, however, considerably less developed, such that the overall appearance more closely resembles a long snouted Peckoltia than a dwarf sized Panaque (Panaqolus stay considerably smaller than their large food competitors). Male Panaqolus show at least during spawning season heavy growth of odontodes on the caudal peduncle, a trait they share with Peckoltia and, a little less developed, with some Hypancistrus. Comparable growth cannot be found in Panaque.

The Parancistrusgroup
Common trait of this group is a membrane attached to the back end of the dorsal fin. Usually it connects dorsal and adipose fin, while in Baryancistrus, it does not. Most species/genera have quite massive heads.

Especially apparent is the massive, half rounded head in Parancistrus. Adult specimen often appear to be half head. In conjunction with the dorsal fin membrane and comparably huge gill openings, Parancistrus are easily identified.

Not just that big is the head in Oligancistrus, which, in return, have an even stronger developed membrane connecting dorsal and adipose fin. This membrane is sometimes developed such that dorsal and adipose fin are connected to one huge, sail-like fin. The gill openings of Oligancistrus are developed normally and allow for differentiation from Parancistrus at first sight. Quite unique is, in addition, the dentition of Oligancistrus: while in most loricariid catfish the teeth in lower and upper jaw are of comparable size, the teeth in the upper jaw are considerably longer in Oligancistrus. The exact opposite is seen in Hypancistrus.

Finally, Spectracanthicus is found in this group. These are easiest told from the other members of this group by their head shape. The species of this genus resemble Leporacanthicus, especially based on the head profile and the overall slender appearance. In contrast to Leporacanthicus, however, the species of Spectracanthicus do not show the fimbriae at the upper lip typical for the former. Also, the membrane of Spectracanthicus is not present in Leporacanthicus.

Based on body shape alone, it is difficult to find telltale characteristics for Scobinancistrus, as they show the 'typical' body shape of a loricariid catfish, as is found, for instance, in Hypostomus. Young individuals might even be mistaken for a slender Peckoltia at first sight. Nevertheless, as ever so often, a hobbyist that has seen a Scobinancistrus can spot its congeners immediately. Fortunately, there is one trait that allows identification of Scobinancistrus also for the less experienced. As is often the case, a look into the mouth of a fish is helpful. Of all known loricariid catfish, Scobinancistrus have the most reduced dentition, possessing not more than 3 and 4 long, spoon shaped teeth per jaw, respectively. In contrast to Panaque and Panaqolus, however, these spoon shaped teeth do not hint to wood eating, but are believed to be best suitable for eating molluscs. Well developed odontodal growth is not present, the evertible gill odontodes identify this genus as member of the Tribe Ancistrini, however.

Certainly not a member of Ancistrini is the genus Aphanotorulus (sometimes regarded as the Hypostomus frankei - group), which is immediately recognized by the lack of evertible cheek odontodes. All species of this genus share the whitish-grey base colour with black spots, which is almost sufficient to identify this genus. Additionally, males grow heavy odontodes covering the whole body during spawning season, considerably heavier than is found in certain Peckoltia species.

In contrast, Squaliforma (the Hypostomus emarginatus - group) species do not show this growth of odontodes (or if they do, it is found considerably later in the development, when sheer body size is sufficient for differentiation), but share the basic colouration with Aphanotorulus. The shape of the caudal fin can also be used for identification, as the lower lobe is considerably longer than the upper one in Squaliforma. Final certainty can then be achieved by checking the upper lip: it shows some short fimbriae (as found in Leporacanthicus, but less developed) in Aphanotorulus, the lips of Squaliforma are smooth. While Aphanotorulus will stay comparatively small with about 15 cm TL, Squaliforma can (and will) reach considerable sizes of 40-50 cm TL.

As third genus with comparable colouration, Isorineloricaria (which should be termed Hypostomus spinossissimus according to present scientific status) should be mentioned. However, they are easily told apart from the other two: species of the genus Isorineloricaria have a unique, extremely long tail which is more reminiscent of Loricariinae (whiptail catfishes) than of Loricariidae (in the sense used in this contribution). Also, Isorineloricaria show considerable odontodal growth, especially in males. With these characteristics, Isorineloricaria should be easily identifiable from other genera.

Members of the genus Cochliodon (or the Hypostomus cochliodon group) are easiest recognized by their head profile. They closest resemble species of the genus Hypostomus, but Cochliodon usually appear to be stockier in direct comparison. Unfortunately, what was stated before for Hemiancistrus, does apply to Hypostomus even more. This 'genus' so obviously collects species belonging to several genera, that a listing of characteristics specifying Hypostomus would result in a description applicable to just about any other loricariid catfish lacking evertible gill odontodes.

Fortunately, Cochliodon are easier identified: they should not have evertible gill odontodes (that is easily found out with the fish in hand), and additionally, the dentition should be comparable to that of Panaque and Panaqolus, thus having few, spoon shaped teeth in acutely angled jaws. This is due to comparable feeding habits: just like Panaque and Panaqolus, the species of this genus represent wood eaters, which, provided fate allows for it, take life easy and first eat the plants in their aquarium before returning to munching on wood.

The Pterygoplichthysgroup
This group of large growing catfishes is rather easily discerned from other genera, as the genera of this group have the highest number of soft rays in their dorsal fins. The resulting, almost sail-like dorsal fin makes them attractive, it should be kept in mind, however, that the fishes of these genera rarely remain under 50 cm TL.

The largest dorsal fins are found in the genus Glyptoperichthys (also regarded as the Pterygoplichthys lituratus group), the members of this genus having 12-14 soft rays in their dorsal. Unmistakable in Glyptoperichthys is the so-called supraoccipital-ridge, which is formed by a certain bone of the skull. This ridge is immediately visible between eyes and insertion of dorsal fin, and grows more prominent with age.

This ridge is the easiest way to differentiate Glyptoperichthys from Liposarcus (at present, only accepted as the Pterygoplichthys multiradiatus group). While the dorsal fin ray count is identical, Liposarcus do not show the ridge between eyes and dorsal fin that is present in Glyptoperichthys, though the denominating bone is of course also present in Liposarcus.

Contrary to the two aforementioned genera, Pterygoplichthys have yet to play a role in the hobby. Their body shape strongly resembles that of Liposarcus and Glyptoperichthys, a supraoccipital ridge is not present as is found in Liposarcus. Unambiguous identification is possible through dorsal fin ray count: in contrast to all other members of this group, Pterygoplichthys have 10-11 soft rays in their dorsal. This is sufficient to tell this genus from all other loricariid catfish genera (with the exception of Megalancistrus, which is easily identified based on odontodes), since all other known genera usually have less soft rays in the dorsal.

The Rhinelepini
The genera in this group are probably the most archaic looking members of loricariid catfish. The most prominent similarity of these genera is, besides some interesting specialities only visible in dead fish, the lack of an iris flap. While (almost) all loricariid catfish have a skin flap used to adjust the light intensity reaching the eye, the iris of Rhinelepini is round. Additionally, they (with one exception so far) lack an adipose fin present in almost all other loricariid catfish. Finally, the robust and archaic looking bone plates should be mentioned. These are rather large and appear bulky.

The two at least somewhat known genera Rhinelepis and Pseudorinelepis share the lack of an adipose fin. The exact differentiation of the two genera is easiest in direct comparison: while Pseudorinelepis have a comparably steep head profile reminiscent of Cochliodon, this profile is flatter in Rhinelepis. Rhinelepis appear to be even more heavily armoured than Pseudorinelepis, which is probably due to the conspicuous grooves between the large bone plates, best visible in adult fish. Both genera belong, together with Panaque, to the most bulky looking catfish if adult.

Pogonopoma seem to be almost slender if compared the other two genera, albeit not exactly fragile. Also the fins appear to be larger in comparison. Aside from this, there are little differences apparent for the hobbyist.

Finally it is noted that at least Pseudorinelepis shows some colouration, while the other species of this group only contest for the more beautiful grey-black colour.

A special place is taken by the genus Corymbophanes, which at first sight might appear to be reminiscent of a Chaetostoma, based on the rather large head and the appropriately dimensioned sucker mouth. In contradiction, however, Corymbophanes do not possess an adipose fin and also the iris flap is missing, a trait found only rarely in loricariid catfish. This combination of characteristics is unique among loricariid catfish and precludes addition of Corymbophanes to any of the subgroups presented here.

The author is deeply indebted to Walter Lechner for his considerable support in correcting the original German version of this contribution (in terms of language as well as scientific facts) which was published as part of the 2009 L-Welse.com calendar. Considerable support in proof-reading the German version by Daniel Konn-Vetterlein is also gratefully acknowledged. Any inaccuracies (or mistakes) in the translation as well as in the original publication are solely due to the author; some additions have been made with respect to the original publication during the process of translation.

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