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Amazon Redtail Catfish

Amazon Redtail Catfish Greenfield Valley Sport Fishing Specimen Lake 2 Hua Hin Thailand

© by Günter & Muriele Fritsche
Greenfield Valley Sport Fishing Specimen Lake 2 Hua Hin Thailand

Name: Amazon Redtail Catfish (pirarara)
Species: Phractocephalus hemioliopterus
Thai name: ปลาอเมชอนเรดเทล (Bplaa amazon redtail)
Max length: 2m (6.561ft)
Max weight: 100kg (220lb)
IGFA record: 56kg (123lb)
Stocked to: 45kg (99lb)
Diet: Fish, squid, shrimp, fruit, vegetables, scavenger, he eat almost any food item
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Amazon Redtail catfish breed in the Greenfield Valley Sport Fishing Specimen Lake 2

Because we have an excellent water quality and Sandy underground in our Lake our Redtails breed. They build nests on the shores of Lake approx. 0.8 m wide and approx. 20-30 cm deep. We have therefore every year many young Amazon Redtail catfish in our Lake. We sell many Redtail catfishes each year to fish farms or friendly fishing lodges in Thailand.

Redtail Catfish Greenfield Valley Sport Fishing Specimen Lake 2 Hua Hin Thailand

This Amazon Redtail Catfish is born in our Lake

Introduction

The redtail catfish, Phractocephalus hemioliopterus, is a pimelodid (long-whiskered) catfish named for its red (male) or orange (female) caudal fin. In Venezuela it is known as cajaro and in Brazil and even in a few parts of Bay of Bengal it is known as pirarara. It is the only extant species of the genus Phractocephalus. This fish originates from South America. Despite reaching a large size (up to 200cm / 6.561ft), this fish is to our regret a common aquarium fish.

Lundberg et al. (1988) described a large catfish skull from the upper Miocene Urumaco Formation, Falcón State, Venezuela. Based on characteristics known at the time, the fossil was assigned to the extant species Phractocephalus hemioliopterus (Bloch & Schneider, 1801), family Pimelodidae. While the 1988 paper was in press a nearly complete and extraordinarily well preserved cranium came to light and briefly noted (Lundberg et al., op. cit., p. 138). Now we have had the opportunity to examine and assess the details of that specimen. In addition, several more Urumaco specimens of Phractocephalus Agassiz have been collected that contribute significant new information on this catfish. Comparisons of these additional fossils with modern specimens (Aguilera, 1994, and herein) show that the Urumaco Phractocephalus is taxonomically distinct from modern P. hemioliopterus. Well-preserved fossils of Phractocephalus have also been reported in the upper Miocene Solimões Formation in Acre, Brazil (Latrubesse et al., 1997; Bocquentin-Villanueva, Jégu & Brito, 1997), and fragmentary material is preserved in the middle Miocene La Venta fauna of Colombia (Lundberg, 1997, 1998). The Acre fossil is being named and described by J. Bocquentin-Villanueva, M. Jégu and P. Brito. Those worker’s and our comparisons of the Urumaco and Acre fossils reveal that the latter represents a second fossil species of Phractocephalus. Accordingly, in this paper we name and diagnose the Urumaco Phractocephalus as a new species. Phractocephalus has been considered monotypic. Modern P. hemioliopterus has a wide distribution in the lowland, meandering rivers and lagoons of the Orinoco, Amazon and Essequibo basins. This species, known as the “cajaro” in Venezuela and Colombia and “pirarara” in Brazil, is one of the most distinctive and important food and ornamental fishes in South America. Based on the strong overall similarity between modern Phractocephalus and available fossil specimens from Urumaco, Lundberg et al. (1988) hypothesized that P. hemioliopterus is a long-lived species with no detectable morphological change since the late Miocene. The additional specimens show that is not the case. The modern and fossil specimens are closely similar in most details, including many characters that are uniquely derived among catfishes, yet these are demonstrably distinct species. The revised taxonomic status of the Urumaco fossil Phractocephalus does not alter its biogeographic significance. This fossil catfish provides direct evidence for former biotic and riverine connections between the Orinoco watershed and the Caribbean coastal region of South America (Lundberg et al., 1988; 1998; Díaz de Gamero, 1996). Thus, the Urumaco and Acre fossils expand our knowledge of the diversity of Phractocephalus over time and space.

Locality, geological context and age

The sample area (Fig. 2) includes the following named localities: El Mamón, Tío Gregorio, Corralito and El Hatillo, all north of the town of Urumaco, Falcón State, northwestern Venezuela. The geological units from which the specimens were obtained are the middle and upper members of the Urumaco Formation of Venezuela. These units have been recently summarized in the Léxico estratigráfico de Venezuela (1997).

The middle member of the Urumaco Formation consists of claystone and sand. The gray claystone is microfossiliferous, and the brown claystone contains vertebrate remains such as reptiles, mammals, marine and freshwater fish, and also coprolites and wood (Díaz de Gamero & Linares, 1989). The limestone changes from conchiferous sandstones to consolidated coquina limestone. In the lower half of this middle member, an abundant and diverse marine mollusk fauna exists in a sandy matrix. This matrix also contains elasmobranch teeth and teleostean otoliths. The paleoenvironments are interpreted as inner sub-littoral and coastal lagoon enviroments with riverine and estuarine influence (Díaz de Gamero, 1996).

The upper member of the Urumaco Formation also comprises gray to brown often limey claystone with thin intercalated and locally conchiferous sandstones. The uppermost layer is referred to as the “capa de tortugas” because of its abundant remains of the turtle Bairdemys Gaffney & Wood. Several localities and levels have concentrations of vertebrate fossils. The vertebrate fauna includes marine, estuarine and freshwater fishes, terrestrial, freshwater and marine turtles and crocodilians, and terrestrial and aquatic/semiaquatic mammals (Sánchez-Villagra et al., 2003). The paleoenvironments were tropical near shore marine to low coastal savannas with freshwater rivers.

 

Description

See Lundberg et al. (1988) for description of neurocranium (MCN.USB 72-85 PB) and additional measurements. The following information is provided by the holotype and recently obtained specimens.

Neurocranium, dorsal aspect (Fig.4a). Outline form of skull approximately rectangular, width across lateral ethmoids equal to width across sphenotics, and these widths slightly less than maximum width across pterotic wings; width across pterotics contained 2.25 times in (45% of) dorsal skull length from mesethmoid tip to posterior edge of supraoccipital process. Surface mostly flat but margins curved slightly downward and dorsal midline increasingly arched posteriorly. All bones ornamented with coarse reticulating ridges and circular pits and some longitudinally elongate ridges and grooves, except for olfactory capsules and extremities of mesethmoid cornua.

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Mesethmoid broad, mushroom-shaped, anterior margin scarcely emarginate (entire in MCN.USB OL-2142), otherwise gently rounded; cornua stout, pointed, little recurved and reaching laterally to a parasagittal line projected before palatine condyle. Mesethmoid without traces of anterior cranial fontanelle. Lateral ethmoid projecting anteriorly into olfactory capsule region; orbital margin short, gently concave, antorbital process a slight curved bulge; contact with sphenotic a long, nearly straight suture running obliquely from skull roof margin behind orbit to frontal near anterior cranial fontanelle. Olfactory capsule floored by mesethmoid and lateral ethmoid. Nasal and infraorbitals unknown.

Frontal flat to slightly concave, confined to center of skull roof, laterally suturing to and excluded from skull-roof margin by lateral ethmoid and sphenotic. Anterior cranial fontanelle present as reduced circular foramen in a midline pit at transverse level of sphenotic-lateral ethmoid-frontal junction (fontanelle obsolete in MCN.USB OL-2142). Frontal ornamented mostly with reticulating ridges and circular pits, except near midline posterior to cranial fontanelle about 5 – 6 parallel longitudinally oriented ridges and grooves.

Sphenotic very large, twice the width of adjacent frontal, approaching a parallelogram in form, broadly sutured to lateral ethmoid, frontal, supraoccipital and pterotic; free lateral margin with a gently convex bulge but lacking prominent postorbital process. Pterotic with angular wing projecting from posterolateral corner; broadly contacting sphenotic, supraoccipital, extrascapula and supracleithrum, the last joint horizontally elongate suggesting limited mobility to dorsoventral axis.

Supraoccipital unusually large, flask-shaped; contacting frontals, sphenotics, extrascapulars, supracleithra and anterior nuchal plate (the last by inference from structure of posterior process and similarity to congeneric species). Expanded part of supraoccipital posterior process is posterior to occipital wall and articulations with upper shoulder girdle elements; process long, covering Weberian complex. Process with broadly rounded lateral and posterolateral margins, ornamented part posterior margin emarginate to truncate across midline, plus a projecting unornamented shelf that would form a lap joint with anterior nuchal plate. Ornamentation of supraoccipital mostly irregular but ridges and pits loosely arranged in 5 or 6 outer concentric rows. Dorsal surface flat behind frontals, then becoming convexly arched along midline to posterior margin, laterally sloping downward concavely to margins of posterior process; cross-sectional shape depressed “bell shaped.”

Extrascapula an ovoid plate isolated from skull margin by surrounding pterotic, supracleithrum and supraoccipital. Supracleithrum preserved in holotype on right side where broken posterolaterally; expanded as roughly lozenge-shaped plate, ornamented as the skull roof; horizontally elongate, weak sutural joint with pterotic and extrascapula; arthrosis style with supraoccipital indeterminate.

Neurocranium, ventral aspect (Fig.4b). Mesethmoid visible ventrally only as flattened, narrow band, anterior to vomerine tooth patch, to which premaxillae (not preserved) articulate; mesethmoid cornua not downwardly deflected. Vomer dominated by massive median tooth plate, approximately pentagonal form, surface concave upward and completely covered by minute pediculate tooth-attachment bases (no teeth preserved). Vomer expanded antrolaterally in front of tooth plate to suture with mesethmoid and lateral ethmoids; tapering posterior limb deeply sutured with parasphenoid.

Palatine condyle projecting prominently from lateral ethmoid, very long and in horizontal plane, convex anteriorly, nearly straight laterally, abruptly truncate posteriorly. Prominent, thin, horizontal “orbital shelf” arises on ventral surface of lateral ethmoid just posterior to palatine condyle and lateral to vomer. “Orbital shelf” continuing onto orbitosphenoid, parasphenoid and prootic to terminate ventral to trigeminofacial foramen; along lateral ethmoid and orbitosphenoid “orbital shelf” is the surface of origin for adductor arcus palatini muscle. Orbitosphenoid dominated by “orbital shelves,” widest anteriorly, about 75% of skull width across lateral ethmoids, narrowing posteriorly to about 45% of skull width across sphenotics at level of hyomandibular facet. Foramina of orbitosphenoid deeply situated and indeterminate. Parasphenoid median stem broad, center of parasphenoid marked by medially converging pair of low ridges and elongate roughened surfaces (associated with contact of anterior branchial arches); parasphenoid weakly sutured to prootics, deeply sutured to basioccipital, indeterminate contact with pterosphenoid.

Anterior half of ventral surface of sphenotic planar and bare; posterior half of sphenotic sharply elevated laterally, forming anterior two-thirds of elongate, horizontal, trough-like hyomandibular facet that runs mediolaterally to sphenoticpterotic suture near skull roof margin, then along edge of pterotic. Hyomandibular facet on pterotic followed at rightangles by another articular facet, short, flat-faced and ventrally buttressed, for posterodorsal corner of hyomandibula. Neither pterosphenoid nor prootic participate in hyomandibular facet or other articulation with hyomandibula.

Medioventrally adjacent to hyomandibular facet, sphenotic, pterotic and prootic together form roof of ovoid, shallow subotic fossa.

Prootic side wall flat dorsal to contact with parasphenoid; position of matrix-filled trigeminofacial foramen indicated by semicircular notch in anterior border of prootic and sharp edged terminus of “orbital shelf” ventral to foramen. Pterosphenoid largely obscured by matrix but no evidence that it is more extensive than in modern species where it is restricted as a small quadrangular element between the prootic, sphenotic and orbitosphenoid.

Basioccipital weakly sutured to exoccipital and prootic; vertebral-like joint with first centrum. Articulation site on basioccipital for ossified Baudelot’s ligament elevated and rugose. Exoccipital weakly sutures with basioccipital, prootic, pterotic and epioccipital; contributing small dorsal process to cranial articulation with Baudelot’s ligament; vagal foramen large, circular, ventrally directed, centered on a vertical through the anterior edge of basioccipital-Baudelot’s ligament joint. Baudelot’s ligament of supracleithrum ossified and heavy; round in section medially near contact with basioccipital and exoccipital. Exoccipital and epioccipital forming sharp posterolateral corner of braincase that vertically buttresses expanded cranial articulation of pteroticsupracleithrum. Anterolateral face of epioccipital concave and weakly sutured to pterotic. Posterior end of pterotic wing produced and expanded ventral to cranial articulation of supracleithrum. Ventral side of supraoccipital posterior process with strong median vertical keel.

Hyomandibula broad and deep, sutured to preopercle via lateroposterior flange, and metapterygoid via wide anterior process; anteriorly sutured and posteriorly synconchondrally jointed to quadrate. Cranial articulation of hyomandibula including slender anterodorsal process abutting weak ridge on sphenotic in front of hyomandibular facet; long, gently rounded condyle articulating with hyomandibular facet of sphenotic and pterotic; plus short, vertically-truncate posterodorsal surface articulating with pterotic behind hyomandibular facet. Lateral face with low, oblique rise between anterior process and preopercular flange, marking attachment limit of inner bundles of adductor mandibulae muscle. Low crest on medioposterior edge ventral to pterotic articulation, otherwise no enlarged articulating processes or muscle origin crests dorsal to opercle condyle. Opercle condyle centered slightly above midpoint on posterior margin; condyle twice as deep as wide. Lateral foramen of facial canal centrally located on anterior surface of adductor muscle crest at level of opercle condyle; medial foramen of facial canal anteriorly located above adductor arcus palatini crest. Medial face with centrally located vertical and crescentic adductor arcus palatini scar more prominent than in modern P. hemioliopterus but is shape and placement similar.

Preopercle sutured to quadrate in addition to hyomandibula; lateral face shallowly concave forming fossa for posterior sections of adductor mandibulae muscle; posterior margin raised in a gentle curve and likely with sensory canal but no discernable lateralis pores; no evidence of external foramen for symplectic canal, but medial foramen of symplectic canal present between quadrate and preopercle.

Quadrate lateral face mostly shallowly concave; anteroventral blade broadly sutured to metapterygoid; mandibular condyle broad and strongly bilobed flanking central saddle, medial lobe of condyle braced by vertical buttress.

Anterior vertebrae (Fig.4b). First centrum articulated to basioccipital and deeply sutured to compound or Weberian complex centrum (2-4). Aortic groove open along midventral line, flanked by low parallel ridges along first and compound centra; broken before centrum of vertebra 5. Weberian complex lacking prominent mid-dorsal vertical lamina; neural arch-spine complex incompletely preserved but anteriorly projecting to contact supraoccipital and exoccipitals. Indistinct pieces of tripus and low os suspensorium remain in place; anterior limbs of transverse processes meet compound centrum at right angle, wide and thickened laterally, broadly contacting ventral articulation flange of supracleithrum; vertebra 5 indeterminate.

Dorsal articulating process of cleithrum bifid, anterior limb longest, and overall similar in size to postcleithral process; postcleithral process deep and nearly equilaterally triangular, coarsely ornamented especially along ventral and ventrolateral edges lateral to articulating fossa of pectoral spine. In ventral view outward bulge of cleithrum in transverse alignment with posterior limit of articulating fossa of pectoral spine. Mesocoracoid not preserved but elevated surface near dorsal edge of coracoid shows its articulation site. Coracoid keel strongly elevated proximally, extending about midway to pectoral symphysis; coracoid keel divides jointed horizontal limbs of cleithrum and coracoid into equal halves; two parallel ridges run toward midline horizontal limbs of coracoid.

Pectoral spine shaft depressed, in section more ovoid than quadrangular, mostly covered by coarse, elongate and anastomosing ridges and grooves (neither mesh-like nor finely-striate); anterior dentations erect, blunt, none strongly antrorse, relatively heavy and about half as numerous as posterior dentations; posterior dentations erect and irregularly spaced, some transversely widened but not exceptionally flattened, sharper and fewer than anterior dentations; anterior and posterior dentation rows without deep trenches and flanking ridges; no anterior distal serrations; spine tip bluntly pointed; spine base robust but details indeterminate.

Discussion

The pimelodid genus Phractocephalus has long been regarded as monotypic. The morphological variation among modern and well-preserved fossil skulls and some postcranial elements indicates that Phractocephalus comprises three species: P. hemioliopterus, †P. nassi and the unnamed Neogene Acre Phractocephalus. These species are differentiated by well-preserved characteristics of dermal bone ornamentation and enlargement of the casque-like skull roof and occipito-nuchal bony plating. The Phractocephalus from the middle Miocene, Colombian La Venta fauna is too incompletely known (partial mesethmoid and partial pectoral spine) to assess its species status. Despite this new understanding of greater taxic diversity, the species of Phracto cephalus are closely similar in most details of their highly apomorphic cranial and pectoral-fin morphology. The Late Miocene †P. nassi and the Acre fossil give a minimum age of about 8 or 9 Ma for the origin of the distinctive osteology of Phractocephalus and at least some species diversification within this small clade.

A thorough analysis of phylogenetic relationships among the species must await a detailed description of the Acre species. However, both †P. nassi and Acre species have more hypertrophied skull and occipito-nuchal elements than modern P. hemioliopterus. The expanded dorsal armor plating can be interpreted as a synapomorphy uniting the two Miocene species. In this light the less extensive skull roof of modern P. hemioliopterus might be either a retained primitive condition within the genus (it is still a more derived condition than found in all other extant pimelodids), or a secondary reduction. Furthermore, in P. hemioliopterus the full reticulating ridge and pit style of dermal bone ornamentation is more derived than that of the fossils which retain more longitudinal ridges and groove ornament.

Despite its uncertain systematic placement within the genus, the La Venta Phractocephalus provides a minimum age of ca. 13.5 Ma for the genus and its sister group Leiarius Bleeker + Perrunichthys Schultz (Lundberg et al., 1988, 1991; Nass, 1991).

Today no Phractocephalus live west or north of the Andes or Venezuelan coastal ranges. The biogeographic significance of Late Miocene Phractocephalus from the northern Venezuelan Urumaco site was discussed by Lundberg et al. (1988) and subsequent authors (Aguilera, 1994; Lundberg, 1997, 1998; Sánchez-Villagra et al., 2003). Recognizing the Urumaco Phractocephalus as a distinct species does not alter the obvious conclusion that this catfish marks a former large freshwater connection between the Caribbean coastal region and the Orinoco system. Other Urumaco fossils show the same biogeographic relationship: mata-mata turtles (Chelus Dumeril), freshwater iniid dolphins, crocodilians (Caiman Spix), freshwater sciaenids (Plagioscion Gill), indeterminate doradids, loricariids, pimelodids and serrasalmine characins. The phylogenetic relationships of many modern endemic freshwater fish species or genera of the Maracaibo Basin also corroborate a former link to the Orinoco and more broadly with the Amazon and Magdalena system. Examples of these among the Pimelodidae are Perrunichthys perruno Schultz, sister to the OrinocoanGuianan-Amazonian genus Leiarius; Platysilurus malarmo Schultz and Cheirocerus abuelo (Schultz), belonging to monophyletic genera with species in the Orinoco, Amazon and Guianas; and Megalonema psammium Schultz and Sorubim cuspicaudatus Littmann, Burr, & Nass (belonging to genera with species in the Orinoco, Amazon, Guianas, Magdalena and Paraná).

The foregoing biotic relationships correlate well with current models of Neogene landscape and drainage evolution in northern South America. Rod (1981), Lundberg et al. (1988), and Díaz de Gamero (1996) discussed evidence for a major outlet of a paleo-Orinoco system into the Caribbean from northwestern Venezuela. A mounting body of evidence has now been presented for a long persistent, large river system originating far south in western Amazonia that flowed north in the Andean foreland basin (Hoorn, 1993, 1994 a, b, c; Hoorn et al., 1995; Lundberg et al., 1998). This “Paleo-Amazon-Orinoco” river system would have contained a common freshwater fauna including fish species represented as fossils from Urumaco (Aguilera & Rodrigues de Aguilera, 2003; Sánchez-Villagra et al., 2003). At times marine and estuarine conditions extended southward into the Andean foreland basin from the Caribbean (Hoorn, 1994 a, b, c; Monsch, 1998) thus providing some opportunities for marine taxa to penetrate far into the South American continent (Lovejoy et al., 1998). Sometime in the Late Miocene, the rising mountain divides of the Eastern Andes and Coastal Cordilleras closed the Caribbean outlet of the “Paleo-Amazon-Orinoco” system. Concomitant or subsequent to the isolation of the coastal region of Urumaco and Falcón State much of the former freshwater biota disappeared.

Additional fossil pimelodid, doradid, loricariid and characiform fishes from the Urumaco fauna are now available for study and should provide more information on the intriguing biotic and landscape histories of northern South America.

The paleo-environments within the Urumaco Formation are a complex mixture of freshwater, estuarine and marine. Deposition occurred on a relative narrow coastal plain. There is no indication of major reworking of fossil remains. Fossils of the “cajaro” catfish (†Phractocephalus nassi) are often associated with remains of “sierra” catfishes (doradids), gavialids (Ikanogavialis Sill, Gryposuchus Gürich), crocodilians (Purussaurus Barbosa-Rodrigues, Mourasuchus Price), “arrau” turtles (Bairdemys Gaffney & Wood), sirenids (indeterminate dugongid) and “tonina” freshwater dolphin (indeterminate iniid). This entire fauna is relatively common in the freshwater facies from the Urumaco Formation, especially in the upper member. Present also in this assemblage are fossils of coastal fishes such as, sea catfish (Arius Valenciennes, Bagre Cloquet, Sciadeops Fowler) and sawfish (Pristis Linck) that often.

© by Günter & Muriele Fritsche
Greenfield Valley Sport Fishing Specimen Lake 2 Hua Hin Thailand
 

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