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LESLEY S. DE SOUZA, DONALD C. TAPHORN & JONATHAN W. ARMBRUSTER. 2019. Review of Ancistrus (Siluriformes: Loricariidae) from the northwestern Guiana Shield, Orinoco Andes, and adjacent basins with description of six new species. Zootaxa, Volume 4552, Number 1: 1-67.

Abstract:
The Orinoco Andes and northwestern Guiana Shield (Essequibo, Orinoco, Branco, and upper Negro) were found to contain 11 species of Ancistrus, six of which are new. We additionally examine A. brevifilis from the Río Tuy of Venezuela and A. trinitatis from the island of Trinidad. The species in the region can be broken up into dorsoventrally flattened species (A. leoni new species, A. lithurgicus, and A. macropthalmus), white to yellow-dotted species (A. kellerae new species, A. nudiceps, and A. patronus new species), wide-jawed species (A. amaris new species and A. yutajae new species), and white-spotted species (A. brevifilis, A. leucostictus, A. trinitatis, A. saudades new species, and A. triradiatus). Distributions of Ancistrus support the Proto-Berbice hypothesis as A. saudades is found in the upper reaches of the Ventuari, Caura, and Caroni rivers, which were thought to have once flowed into the Proto-Berbice. In addition, although A. nudiceps does not appear to have split once the Takutu River was captured by the Branco, the progenitor of A. leucostictus and A. saudades did speciate with the populations on either side of the Rupununi Portal differing by 7% sequence divergence of the mitochondrial Cytochrome b gene. Besides the descriptions of the new species, we redescribe the others occurring in the area, and adjacent watersheds. We provide a key for their identification, and a preliminary hypothesis of relationships based on DNA sequences of the few species for which tissue samples are available.

https://www.mapress.com/j/zt/issue/view/zootaxa.4552.1

Another result of this paper is that it makes a synonym of

? I thought that was named after a Harry Potter spell.

Thanks, Lee. By chance, do you have a copy? If so, can I get a copy from you?

Cheers, Eric

Hi Eric,
No copy at hand yet. Hopefully one will be available later today. Will let you know.
Take care.
Lee

Now available on ResearchGate:
https://www.researchgate.net/publicatio ... ew_species

@Jools, This paper measures head shape in a similar way to how we measured head angle when trying to sex @Jac 's chameleon whiptails (Here). Main differences are that the angle tip is moved here to accommodate the fleshy face of Ancistrus, and I used the widest points on the head (at operculum) as landmarks, rather than the fronts of the orbits.

Cheers, Eric

Interesting! @Shane will like this too. The paper might include and - will need to read!

Cheers,

Jools

Here is the key from the paper: (sorry for the multiple posts, I'm experimenting with user interactivity here):

Key to the species of Ancistrus from the northwestern Guiana Shield, Orinoco Andes, and adjacent basins

1. No well-defined dark spots on fin spines, fin rays or fin membranes alternating with lighter spots; tiny (the largest usually less than 1/2 the diameter of the pupil of eye) white, yellow or greenish dots on abdomen, sides, dorsum or fins when alive, usually lost after some time in preservative in which case they may appear entirely dark. . . 2

• 1’. Spines, rays or membranes of fins with alternating dark and light spots, often arranged in rows; body and/or fins usually (but not always visible in preserved material) with larger white spots or blotches, some of which are larger than diameter of pupil of eye. . . 7

2. Body dorsoventrally flattened. Eyes placed dorsally or slightly dorsolaterally. Last plate in median series below adipose fin just slightly taller than wide. . . 3

• 2’. Body deep. Eyes placed mostly laterally. Last plate in median series below adipose fin about twice as tall as wide. . . 4

3. Medial section of the interorbital space higher than orbital ridge. Plated area of the snout of nuptial males pointed medially. Pelvic fin reaching to nearly the end of the anal fin when both fins are adpressed. . . Eigenmann, 1912

• 3’. Orbital ridge higher than medial section of interorbital space. Anterior border of plated area of the snout of nuptial males almost straight transversely). Pelvic fin reaching to just barely beyond base of pelvic fin…
  Ancistrus macrophthalmus
  (Pellegrin, 1912)

4. Least interorbital width divided by dentary length less than 2. . . new species

• 4’. Least interorbital width divided by dentary length greater than 2.25. . . 5

5. Spots only present on head and nape. Edge of caudal fin often broad, gold band. Dark lateral stripe along sides of body with area above darker than below. Pectoral-fin spine with faint, dark spots. In nuptial males, naked area present posteromedially to the medial row of tentacles extending to anterior margin of nasal apertures and only a small plate surrounded by flesh between the nasal aperture and the posteriormost odontodes. . . new species

• 5’. Spots present over the entire body or fins (may be completely absent in preserved specimens). Edge of caudal fin without broad, gold band. Sides uniformly dark, without lateral stripe. Pectoral-fin spine uniformly dark or with small, gold spots. In nuptial males, no naked area present posteromedially to the medial row of tentacles and several plates that abut one another between posterior tentacle and nasal aperture. . . 6

6. Maximum size 138 mm SL. Snout relatively long and spatulate (Fig. 5a), best visualized in nuptial males where the plated region of the snout forms a long, rounded triangle such that the distance between the plates and the tip of the snout (turqoise line in Fig. 5a) is much smaller than the distance between the tip of the plated area and a line drawn between the anterior margins of the orbits (yellow line in Fig. 5a). Tentacles of the snout bifurcating at the start of the snout plates in a V. . . (Müller & Troschel,1849)

• 6’. Maximum size 86 mm SL. Snout relatively short and rounded (Fig. 5b), best visualized in nuptial males where the plated region of the snout forms a broad arc and the distance from the plates to the tip of snout (turqoise line in Fig. 5b) is approximately equal to the distance from the tip of the plates to a line drawn between the anterior margin of the orbits (turqoise line in Fig. 5b), and tentacles of the snout bifurcating at the start of the snout plates in a U. . .
  Ancistrus patronus
  new species

7. Body dorsoventrally flattened. Eyes placed dorsally or slightly dorsolaterally. Last plate in median series below adipose fin just slightly taller than wide. Tentacles on medial portion of the snout in nuptial males in a single column. Few white spots organized in lines down body. Dorsal saddles prominent. . . new species

• 7’. Body deep. Eyes placed mostly laterally. Last plate in median series below adipose fin about twice as tall as wide. Odontodes on medial portion of the snout in nuptial males either transversally straight anteriorly or forming a broad triangle. Spots either absent, few and randomly scattered, or numerous and scattered. Dorsal saddles absent or not very visible. . . 8

8. Abdomen without spots. . . 9

• 8’. Abdomen with white spots. . . 11

9. Spots on caudal fin not organized, often combining across rows to form very elongate spots, sometimes almost half the length of the caudal fin and more than twice as long as wide. . . Eigenmann, 1920

• 9’. Spots on the caudal fin organized into rows, never combining across rows and never more than twice as long as wide. . . 10

10. Males with tentacles that are no greater than eye diameter. Dentary length/cleithral width 23.8–28.4% in specimens greater than 69 mm SL. Minimal interorbital width divided by dentary length less than 2.1. . . new species

• 10’. Males with tentacles much greater than eye diameter. Dentary length/cleithral width 14.4–24.6% in specimens greater than 69 mm SL. Minimal interorbital width divided by dentary length usually greater than 2.1. (The only specimens that overlap with A. amaris do so because of smaller interorbital and cleithral widths, not longer jaws) . . .
  Ancistrus triradiatus
  Eigenmann 1918 (part)

11. Spots on dorsal fin small and confined to fin rays and not present on membranes (alternating dark and light spots). . . (Günther, 1864)

• 11’. Large white spots on dorsal fin centered on membranes separated by smaller dark interspaces. . . 12

12. Adpressed dorsal fin reaching to at least the middle of the adipose-fin spine. Pectoral-fin spine when adpressed ventral to the pelvic fin reaching the base of the cloacal tube in adults. Relatively larger light spots and narrower dark interspaces on the anterolateral plates and posterodorsal head bones with the interspaces much less than half the width of the spots and at least some spots always visible in this area on preserved specimens (difference generally works on the abdomen as well). . . (Günther, 1864)

• 12’. Adpressed dorsal fin reaching maximally to middle of preadipose plate. Pectoral-fin spine when adpressed ventral to the pelvic fin not reaching the base of the cloacal tube in adults. Relatively smaller light spots and larger dark interspaces on the anterolateral plates and posterodorsal head bones with the interspaces half or greater than the diameter of the spots and the spots often obscured in this region in preserved specimens (difference generally works on the abdomen as well). . . 13

13. Spots on head and abdomen small, more than 15 across abdomen in region posterior to pectoral girdle, spots on snouts of males less than half widths of tentacle bases. . . new species

• 13’. Spots on head and abdomen large, fewer than 12 across abdomen in region posterior to pectoral girdle, spots on snouts of males almost to greater than widths of tentacle bases. . .
  Ancistrus triradiatus
  Eigenmann, 1918 (part)

Great to see it finally published. Have been in touch with Don on this paper for quite some time.
-Shane