taxonID	type	description	language	source
03F14C5518317C32FF5FF954FB2F4728.taxon	type_taxon	Type species: Olmecadrilus tuxtlensis sp. nov.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518317C32FF5FF954FB2F4728.taxon	diagnosis	Diagnosis: Eight setae per segment. One gizzard in segment 5 or 6; esophagus region of segments 9 – 14 with calciferous glands characterized as lateral dilatations or pouches with internal lamellae centrally free. Typhlosole present; intestinal caeca absent. Dorsal and supraesophageal vessels present; last latero-esophageal heart in 13. Meroic, with tufted paired pharyngeal micronephridia in pre-gizzard segments, numerous closed parietal meronephridia in the intestinal segments and last segments with a pair of mesial open megameronephridia. Holandric. Paired tubular prostates opening in segments 17 and 19; male pores in 18. Penial and genital setae absent. Spermathecae opening in the region of segments 7 – 9, with diverticula.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518317C32FF5FF954FB2F4728.taxon	etymology	Etymology: The name of the genus is dedicated to the Olmeca ancient Mesoamerican culture that inhabited the Mexican states of Veracruz and Tabasco.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518317C32FF5FF954FB2F4728.taxon	discussion	Remarks: The main characters that separate Olmecadrilus gen. nov. from Ramiellona are the absence of penial setae and intestinal caeca (both present in Ramiellona) and the last latero-esophageal hearts in segment 13 (in 12 in Ramiellona). Besides, the geographical distribution is almost disjunct, with Olmecadrilus mainly distributed in the states of Veracruz and Oaxaca, north and west of the Tehuantepec Isthmus and Ramiellona inhabiting the Mexican states of Tabasco and Chiapas and the countries of Guatemala, El Salvador and Honduras.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518327C38FF5FFD1DFBF54120.taxon	description	(Figures 1, 2, 3, 4,15 A)	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518327C38FF5FFD1DFBF54120.taxon	materials_examined	Holotype. Clitellate adult from locality 2: IEOL- 681.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518327C38FF5FFD1DFBF54120.taxon	materials_examined	Paratypes. Clitellate adults from localities 1 (complete, IEOL- 679), 3 (complete, IEOL- 6712; fragmented IEOL- 204), 4 (complete, IEOL- 682) and 7 (complete IEOL- 4715) were externally and internally characterized; the following complete adults were externally revised only: locality 3: IEOL- 6713, IEOL- 305, IEOL- 301, locality 5: IEOL- 805, locality 6: IEOL- 311 and locality 8: IEOL- 4735.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518327C38FF5FFD1DFBF54120.taxon	description	Description External. Length: relaxed fixed 183 – 210 mm (mean = 196 mm, n = 3) (Fig. 1 C); contracted fixed 122 – 182 mm, (mean = 146 mm, n = 9); holotype 177 mm, contracted fixed. Width (postclitellar) 3.6 – 4.4 mm (mean = 4.11, n = 13; holotype 4.0 mm). Segments 172 – 268 (mean = 226, n = 12; holotype 177). Pigment dark reddish along the dorsum. Prostomium closed epilobous, in some individuals closed epi-tanylobous due to the continuation of longitudinal grooves (Fig. 1 D). Peristomium with longitudinal annulations that anastomose in some individuals. Secondary furrows absent. Setae eight per segment, visible from segment 2, closely paired along all the body. Setal formula in anterior region (average, n = 12) (aa: ab: bc: cd: dd): segment 10: 5.6: 1: 6.7: 1: 29.5, X = 1.3; segment 30: 5.4: 1: 6.2: 1: 29, X = 1.4; ten segments before anus: 4.2: 1: 4.3: 1: 19.6, X = 1.2. In two examined individuals, setae c and d of last segments move above the mid-lateral level (dorsal); in the other 10 examined individuals, setae d ventral, and under the mid-lateral level throughout the body. Clitellum dark reddish, saddle shaped, extending in 13 – 20 (six ind.) or 13 – 20, ¼ 21 (eight ind.); in the ventral region reaching A, B or AB lines (Fig 1 A, B); dorsal intersegmental furrows recognizable in clitellum of 80 % of individuals. Dorsal pores large, present throughout the body; first small pore in 11 / 12, from 12 / 13 functional and all the same size (n = 12). Spermathecal pores paired in 7 / 8 and 8 / 9, large (Fig. 1 B), in some cases protruding (Fig. 1 A), centered in AB, and measuring 420, 450 microns. Female pores in 14, presetal in B or AB, very small, slit like, measuring 54, 70 microns. Seminal grooves straight, in the lateral walls of a sunken genital zone which extends five segments (16 – 20), and from B to B (Fig. 1 A, B); in the midventral line of genital zone, epidermis is cord-like modified. Two pairs of slit-like prostatic pores on seminal grooves, in the middle of 17 and 19, in some individuals very clear, aligned to AB (Fig. 1 F). Male pores within the seminal grooves in 18, minute, recognized only in the holotype, close to 17 / 18 and aligned to AB (Fig. 1 F). Genital marks: BB ventral region of segments 7, 8 swollen, showing two circular post-setal, midventral papillae just between spermathecal pores, generally well differentiated (Fig. 1 A, B); in some individuals pre-setal region of 9 also swelled. Unpaired mid-ventral papillae, circular to slightly elliptical with a marked circular inner center, located in segments 11 – 14 (Fig. 1 A, B, E) (4 papillae; 8 individuals including holotype); in some individuals only swellings; additional papillae present in other individuals in s. 11 and 15. Internal. Septa 5 / 6, 14 / 15, 15 / 16 and afterwards very thin and membranous; 8 / 9 – 12 / 13 and occasionally 13 / 14 muscular and increasingly thick; septa 5 / 6 – 10 / 11 funnel-shaped and imbricated (Fig. 2 A), in some individuals those of 9 / 10 – 10 / 11 joined by several lateral connective tissue fibers. One large gizzard in 5, extending in segments 7 – 9, 10 (Fig. 2 A), square or slightly cylindrical, measuring (length × wide) 3.3 x 2.8, 3.5 x 2.7 and 3.8 x 3.8 mm. Five pairs of calciferous glands in 9 – 13 (13 ≥ 12 ≥ 11 ≥ 10> 9), as sessile, ventro-lateral sacs (Fig, 2 A, B) that open into the esophagus through a duct; internally each sac with large and numerous lateral and ventral lamellae with free margins (Fig. 2 C, D, E), in larger glands 2 – 3 dorsal vessels are observed in the internal wall, as well as several smaller vessels in lamellae (Fig. 2 D, E); externally, the dorsal region is dark brown colored due to the abundant internal vascularization (Fig. 2 A, B). Intestine begins in 16 / 17 (holotype and 3 paratypes), or (one ind.) in middle 15. A lamina-shaped intestinal typhlosole starts as a small fold in segment 18 or 25; it abruptly reaches its maximal size (occupying 1 / 4, - 1 / 6 of lumen) in segment 31, 32 or 35, continuing with the same shape and size for 70, 143, 145 segments, when it abruptly diminishes its size, ending 50, 59, 73 or 88 segments before anus. Intestinal caeca absent. Single dorsal vessel visible throughout, easily visible from s. 6; in some individuals it is full of blood from s. 15 (Fig. 4 A). Supra-esophageal vessel visible in 9 – 13; in segments 12, 13 very large and full of dark blood. Lateral hearts in 7, 8, 9 and 10; latero-esophageal hearts in 11, 12 and 13. Ventral vessel present. Paired ventral vessels present in 9 – 15; those of 15 thin and ventral; in 14 they are ventrolateral, attached to the floor and next to esophagus; in 9 – 13 located below esophagus (subesophageal), those of 11, 12 and 13 anastomosing with ventral region of corresponding calciferous glands; from vessels of 9, thin lateral branches join ventral wall and septum 9 / 10. Paired clusters of tufted micronephridia in segments 2 – 4; in each side, tufts join a ventral duct that discharges into the mouth (s. 2), just before the pharynx (Fig. 3 A). Ventrolateral septal meronephridia observed in the anterior face of septa of 12 and previous segments. Seven to eight parietal, closed, meronephridia on each side (14, 16 per segment), from segment 13 backwards (Fig. 3 B). Median ventral nephridia of last segments (from 31, 33 segments before annus) larger and with a nephrostome into the preceding segment (Fig. 3 C, D). Holandric. Testes of 10 and 11 located mid-ventrally on the anterior septum; small and bush shaped, joined and covered to the male funnels by coagulum. Male funnels iridescent and plicated, placed at both sides of the mid-ventral line of the posterior septum; funnels of 11> 10. An incipient testicular chamber was observed in some individuals by the lateral joint of septa 9 / 10 and 10 / 11; this chamber is reinforced by some ventral bands of muscular and connective tissue. Male gonoducts difficult to see; double, iridescent, nearly straight, running along body wall in AB and entering body wall in the equator of 18. Two pairs of acinous seminal vesicles in 11 and 12 (Fig. 2 A), respectively fixed to septa 10 / 11 and 11 / 12, and surrounding the esophagus; those of 12> 11. Two pairs of tubular prostates of similar size in 17 and 19, strongly coiled and in general limited to its corresponding segment; in some individuals projecting one segment forwards and backwards (Fig. 4 A); glandular part twofold thicker and c. six times larger than muscular duct. Retractor muscles as thin connective fibers, located in segments 16 – 19, 20, 21 and extending from mid-ventral line to lateral walls. Ovaries one pair, on the floor of 13, with a bushy shape and numerous eggs; female funnels one pair in 13, at both sides of mid-ventral line. Two pairs of similar-sized spermathecae in, respectively, segments 8 and 9, discharging in 7 / 8 and 8 / 9 and strongly fixed to the wall floor by connective tissue; longer axis of the ovoidal ampulla perpendicular to muscular duct (Fig. 4 C); diverticulum sessile, with several spherical seminal chambers projecting from duct, dorsally to ampulla and, in some individuals, with a digitiform like shape (Fig. 4 B). Length of spermathecae 1.36, 1.54, 1.68 mm length per 0.68, 0.98, 1.25 mm wide.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518327C38FF5FFD1DFBF54120.taxon	etymology	Etymology. The name of the species refers to the tropical volcanic region of eastern Mexico, where all individuals were found.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518327C38FF5FFD1DFBF54120.taxon	biology_ecology	Habitat and ecological category. Olmecadrilus tuxtlensis sp. nov. is an epigeic species that inhabits the litter and first 10 cm of soil depth of natural and disturbed tropical rain forests and fallows. The intestinal content indicates that this species prefers organic debris to mineral soil. This species was considered Ramiellona sp. nov. 1 by Fragoso (1997) and Fragoso et al. (2009) and as Ramiellona sp. nov. 18 by Fragoso (2001, 2007).	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518327C38FF5FFD1DFBF54120.taxon	discussion	Remarks: Olmecadrilus tuxtlensis sp. nov. is separated from the other two named species of the genus, Olmecadrilus mexicanus (Gates, 1962) and Olmecadrilus wilsoni (Righi, 1972) (Table 1) by the following characters (first O. tuxtlensis vs. O. mexicanus and O. wilsoni, respectively): dorsal pigmentation: presence vs. absence in both species; prostomium: closed epilobic or epi-tanylobic vs. prolobic and tanylobic; length: 146 mm on average in contracted fixed vs. 96, 116 mm and 77 – 86 mm; calciferous glands: five lateral, sessile sacks in segments 9 – 13 vs. only lamellae in constricted esophagus (no sacks) of segments 9 – 14 (6 s.) and three lateral glands in segments 11 – 13; spermathecal pores: paired in ab vs. unpaired, median and paired in ab; spermathecal diverticulum: one digitiform, sessile vs. one short, digitiform, sessile and two opposite, slightly stalked.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518387C20FF5FFB15FAC646B0.taxon	description	(Figures 5, 6, 7, 15 C)	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518387C20FF5FFB15FAC646B0.taxon	materials_examined	Localities and material Mexico, Veracruz state, Los Tuxtlas Biosphere Reserve (Fig. 15 C): 8) Close to the road to the Laguna Zacatal, at 300 m and 600 m of distance from respectively, Zacatal and Escondida lagoons, municipality of San Andrés Tuxtla. Tropical rain forest, in the first 5 cm of soil depth, 18 ° 35´12.53 " N 95 ° 05´39.49 " W, 208 m asl, two clitellate adults 07 / 11 / 2013, J. A. Angeles and M. de los Santos. Holotype. Complete clitellate adult IEOL- 4734. Paratype. Complete clitellate adult IEOL- 4733.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518387C20FF5FFB15FAC646B0.taxon	description	Description External. Relaxed fixed length: 86 mm in holotype and 95 mm in paratype (mean ¯ x = 90.5 mm, n = 2); width (postclitellar) 1.7 mm (both holotype and paratype). Segments 149, 150 (holotype). Pigment absent. Prostomium tanylobous (Fig. 5 B). Secondary furrows are absent in pre-clitellar segments (Fig. 5 A). Setae eight per segment, visible from segment 2 or 3, closely paired along all the body. Setal formula (average, n = 2) (aa: ab: bc: cd: dd): segment 10: 4.7: 1: 5.6: 1.3: 25.1, X = 1.3; segment 30: 4.9: 1: 5.9: 1.4: 24.5, X = 1.1; 15 segments before anus: 4: 1: 3.7: 1: 9.3, X = 0.6. In both individuals, setae c and d never dorsal before and after the clitellum; in last segments seta d dorsal. Clitellum dark reddish, saddle shaped, from ½ 13 to ½ 20 (both ind.); in the ventral region of segments 13 – 16, 20 reaching B lines whereas genital swelling of seminal grooves limits it to outside B (Fig. 5 A, D). Dorsal pores present throughout the body; first open and functional pore in 12 / 13; in 11 / 12 small and closed. Spermathecal pores paired in 7 / 8 and 8 / 9 (Fig. 5 C), small but clearly visible in AB, measuring 108 microns. Female pores in 14, presetal in B very small, measuring 80 microns. Seminal grooves straight and delimited by a swelling region which extends five segments (16 – 20) in AB (Fig. 5 A, D). Within these grooves there are two pairs of prostatic pores in the middle of 17 and 19, and a pair of male pores above the equator of segment 18, in AB (Fig. 5 D). Circular unpaired genital marks in segment 10, presetal, with a dark center and located in the left and right side (ab) of, respectively, holotype (Fig. 5 C) and paratype; in 14 a presetal (holotype, Fig. 5 A) or postsetal (paratype) midventral swelling. Internal. Septum 5 / 6 extremely thin and before gizzard; septum 6 / 7 also very thin and membranous; septa 7 / 8, 8 / 9 thin and membranous; 9 / 10 and 10 / 11 slightly muscular, 11 / 12 and 12 / 13 the more muscularized (Fig. 6 A); except 5 / 6, all funnel shaped and imbricated in some cases joined by lateral connective tissue fibers. From 13 / 14 and backwards, thin membranous and not funnel shaped. One cylindrical gizzard in 6, but displaced to segments 7 – 9, measuring 1.35 mm length × 0.97 mm wide (holotype, Fig. 6 A). Five pairs of calciferous glands in 9 – 13 of nearly similar size in holotype; in paratype those of 13 and 12 the larger. They are sessile, kidney shaped and ventro-lateral to the esophagus; internal structure characterized by lateral and ventral lamellae with free margins. Intestine begins on 15 / 16 (Fig. 6 A, 7 C). Intestinal lamina-shaped typhlosole starting abruptly as a small fold in segment 19, 20; it gradually increases in size, reaching its maximal size (1 / 10 of lumen) in segment 25 or 30; it ends in segment 111 or 116, 34, 38 segments before anus. Intestinal caeca absent. Conspicuous single dorsal vessel visible throughout (Fig. 6 A, 7 C). Supra-esophageal vessel visible in 10 – 13. Lateral hearts seen in 9 and 10; latero-esophageal hearts in 11, 12 and 13 (Fig. 6 A). Ventral vessel present. Paired latero-ventral vessels seen in 14, coalescing in 14 / 15. Paired tufted nephridia in segment 5, attached to septum 5 / 6; each tuft with a ventral duct that runs anteriorly, probably discharging into the mouth (Fig. 6 B). From segment 14 backwards, six to ten parietal, closed, micromeronephridia (three to five in each side) (Fig. 6 A, 7 C). Median ventral meronephridia of last segments (visible 17 segments before anus) larger and with a clear nephrostome into the preceding segment (Fig. 6 C). Andry in holotype and paratype differed. Paratype 4733 was clearly holandric, with iridescent and plicated male funnels in 10 and 11, located mid-ventrally on the anterior septum of the corresponding segment; although testes were not seen, presence of iridescence in male funnels indicate their presence in both 10 and 11 segments. In the case of the holotype 4734, male funnels were observed in both 10 and 11 segments, although iridescence was observed only in those funnels of segment 11; in addition, testes were only observed in segment 11, suggesting the anterior loss of functional testes, i. e. metandry. Overall, what this could indicate is that metandry has not yet being fixed in this species, and that both holandric and metandric individuals are found within the population. This condition is supported by the difference in the number and position of seminal vesicles observed among paratype and holotype. In paratype 4733 paired acinous vesicles lateral to the esophagus were observed in segments 11 (from 10 / 11) and 12 (from 11 / 12), the latter the greatest; in holotype 4734 only a pair of large acinous seminal vesicles were observed in s. 12, lateral to esophagus (Fig. 6 A). As discussed later, differences in andry could also be due to parasitism. Male gonoducts seen only in holotype in segment 16 and apparently supra-parietal and double. Two pairs of tubular prostates in 17 and 19, strongly coiled with a square shape, and limited to its corresponding segment, the glandular part twofold thicker than muscular duct (Fig. 6 A, 7 C). Ovaries one pair, large, on the floor of 13, with several rows of eggs (Fig. 6 A); female funnels one pair in 13, small, at both sides of mid-ventral line. No ovisacs observed in segment 14. Two pairs of spermathecae attached to the wall floor in segments 8 and 9 and discharging, respectively, in 7 / 8 and 8 / 9 (Fig. 7 A). Longitudinal axis of the ovoidal ampulla perpendicular to muscular duct, which joins it in the middle or lower quarter, and with an overall appearance of an ocarina (Fig. 7 B). Diverticulum sessile or slightly pedunculated, dorsally emerging from the very short duct, just in the joint to ampulla, and characterized by two dorsal and spherical seminal chambers which are partially occluded by the ampulla (Fig. 7 A, B). Length of spermathecae: segment 8: 0.5, 0.7 mm; segment 9: 0.7, 0.8 mm.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518387C20FF5FFB15FAC646B0.taxon	biology_ecology	Habitat and ecological category. Olmecadrilus ocarinus sp. nov. is an endogeic species that inhabits within the soil. It is a scarce species that was only found in a single site of undisturbed tropical rain forest, despite an intensive sampling carried out over several years and in several locations of Los Tuxtlas Mountains. The intestinal content indicates that this species consumes soil mixed with organic debris.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518387C20FF5FFB15FAC646B0.taxon	discussion	Remarks: Olmecadrilus ocarinus sp. nov. is separated (Table 1) from O. wilsoni by the shape of the spermathecae (ocarina shaped ampulla with a single sessile diverticulum with two chambers vs. ovoidal ampulla with two opposite diverticula) and the amount of calciferous glands (five in segments 9 – 13 vs. three in segments 11 – 13); from O. mexicanus is separated by the posterior setae (closely paired through the body vs. quincuaxial in posterior segments), number of anterior spermathecae (two vs. one), and by the position of seminal vesicles (two pairs, in 9 and 12 or one in 12 vs. two pairs, in 11 and 12). By the ocarina shaped spermatheca and the position of seminal vesicles in 11 and 12, the new species is similar to Olmecadrilus tuxtlensis sp. nov.; they are, however, easily separated by size (86 – 95 mm length and 1.7 mm width vs. 122 – 210 mm length and 4.11 mm width), number of segments (149,150 vs. 172 – 268), pigment (absence vs. present) and prostomium (tanylobous vs. closed epilobous, or closed epi-tanylobous). Although only two adult clitellate individuals were found, Olmecadrilus ocarinus sp. nov., shows a within population variability in male gonads, exemplified by the number of functional testes and seminal vesicles. This could be a natural variation or the result of seminal vesicle parasitism by gregarines, as far as presence of gregarine cysts were observed in holotype anterior segments, which also lacked the anterior seminal vesicles and presented an atrophy of segment 10 testes; conservation of a double gonoduct, however, indicates an holandry condition. It is well known that gregarines parasitize earthworms (Edwards & Arancon 2022) and that seminal vesicles are the main organ affected (Bhatia & Chatterjee 1925, Segun 1978); the infection could in some cases destroy the male storage of spermatozoa (i. e seminal vesicles), turning affected earthworms into parthenogenetic clones (Schall 2021).	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518207C25FF5FFC6AFC954018.taxon	description	(Figures 8, 9, 10, 15 B)	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518207C25FF5FFC6AFC954018.taxon	materials_examined	Localities and material. Mexico, Veracruz state, Los Tuxtlas Biosphere Reserve (Fig. 15 B): 3) Close to Los Tuxtlas Tropical Biology Station of the UNAM, slightly forward of junction of north boundary marker of the station and the road to Laguna Escondida, municipality of San Andres Tuxtla. Tropical rain forest with abundance of the palm Astrocarium mexicanum, on a slight slope, in the first 10 com of soil depth, 18 ° 35 ' 15.08 " N, 95 ° 04 ' 36.19 " W. 200 m asl, two clitellate adults, one lacking some anterior segments 07 / 16 / 1984, C. Fragoso and P. Lavelle; two clitellate adults 08 / 10 / 1986, C. Fragoso. 4) 2.8 km from the north limit of Los Tuxtlas Tropical Biology Station of the UNAM, on the road to Ruben Sanchez ranch. Ruiz Cortinez forest, property of Silvio Cabañas, municipality of San Andrés Tuxtla. Tropical rain forest with Astrocarium mexicanum, over dark, volcanic sandy soils with a deep litter layer, in the first 10 com of soil depth, 18 ° 36 ' 57.61 " N, 95 ° 05 ' 35.38 " W. 52 m asl, two clitellate adults 07 / 18 / 1984, C. Fragoso and P. Lavelle; two clitellate adults 10 / 15 / 1985, C. Fragoso. 6) 2.7 km after the north boundary of Los Tuxtlas Tropical Biology Station of the UNAM, and 500 m before the Ruiz Cortinez forest, property of Silvio Cabañas, municipality of San Andres Tuxtla. Tropical rain forest, over dark, sandy soils on a flatland, 18 ° 36 ' 40.51 " N, 95 ° 5 ' 35.52 " W. 90 m asl, three clitellate adults 04 / 03 / 1986, C. Fragoso. 9) On the edge of Laguna Escondida, north of Los Tuxtlas Tropical Biology Station of the UNAM, municipality of San Andres Tuxtla. Disturbed tropical rain forest, close to a site with an abundance of orange trees. Along a slope transect from the lake edge, over sandy dark brown stony soils, under stones and in first 10 cm of soil depth, 18 ° 35 ' 31.90 " N, 95 ° 05 ' 14.58 " W. 160 m asl, one clitellate adult 08 / 11 / 1986, C. Fragoso; two fragmented clitellate adults 08 / 02 / 1986, C. Fragoso. 10) Top of San Martin Volcano, place “ Parador Palmeros ” close to San Andres Tuxtla. municipality of San Andres Tuxtla. Tropical rain forest, in the first 10 cm of soil depth, 18 ° 33 ' 24 " N, 95 ° 12 ' 00 " W, 1300 m asl, two clitellate adults 09 / 24 / 1994, J. Bueno and G. Brown. Holotype. Clitellate adult from locality 4: IEOL- 6717 Paratypes. Clitellate adults externally and internally characterized: localities 3: IEOL- 276; 4: IEOL- 689 and 6718; 6: IEOL- 6719; 9: IEOL- 6720, in regeneration; and 10 IEOL- 6722. Clitellate adults externally revised or checked for spermathecae shape only: localities 3: IEOL- 268, 240 (lacking some anterior segments), 249; 4: IEOL- 6722; 6: IEOL- 6723, 6724; 9: IEOL- 6725, 255; 10: IEOL- 6726.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518207C25FF5FFC6AFC954018.taxon	description	Description External. Length: 60 – 136 mm (mean ¯ x = 85.4 mm, n = 12; holotype 107 mm). Width (postclitellar) 1.6 – 2.8 mm (mean = 2.3, n = 15; holotype 2.3 mm). Segments 162 – 225 (mean = 197, n = 13; holotype 200). Pigment absent. Prostomium open or closed epilobous, in some individuals closed epi-tanylobous due to the continuation of longitudinal grooves (Fig. 8 B). Peristomium with longitudinal annulations. Secondary furrows are characterized in general by one pre and one post setal furrows before clitellum; after it, two pre and two post setal. Setae eight per segment, visible from segment 2, closely paired before clitellum (Fig. 8 A, B, C, D); in the posterior region they become widely paired and conspicuous; seta c and d begin to move to the dorsal region about mid-body; in last segments, setae d completely dorsal, close to mid-dorsal line (Fig. 8 E). Setal formula in anterior region (average, n = 10) (aa: ab: bc: cd: dd): segment 10: 4.7: 1: 8.1: 0.9: 22.3, X = 0.9; segment 30: 6.1: 1: 6.9: 0.9: 22.4, X = 0.9; ten segments before anus: 1.4: 1: 1.2: 0.9: 1.0, X = 0.1. Clitellum dark reddish, saddle shaped, extending in 14 – 20 (seven ind. Fig. 8 A), ¼ 13 – ½ 21 (three ind.) or 14 – ¼ 21 (three ind. Fig. 8 C); in the ventral region reaching B or ¼ BC lines, delimitated in segments 16 – 20 by swelled light bands which run outside and parallel to seminal furrows (Fig. 8 C). Dorsal pores large, present throughout the body; first pore 8 / 9 (three ind.) or 9 / 10 (nine ind.). Spermathecal pores paired in 7 / 8 and 8 / 9 centered in AB (Fig. 8 D); in some individuals very clear and protruding, whereas in others difficult to see, deep inside the intersegment; measuring 86, 101, 110 microns. Female pores paired in 14, presetal outside B, small, measuring 23, 40 microns. Seminal grooves, nearly straight (Fig. 8 A) or parenthesis like shaped (Fig. 8 C), from segment 17 to 19 extending in AB or slightly outside B. Two pairs of prostatic pores in the middle of 17 and 19, at the end of seminal grooves, within spherical, clear papillae, aligned to AB (Fig. 8 A, C). Male pores minute, probably within the seminal grooves in the middle of s. 18. Genital marks. Before the clitellum there are swellings and diffuse to well defined circular papillae in segments 7 to 12 (Fig. 8 D). The more common marks were paired circular papillae of different size, and centered in ab observed in segment 10 (nine ind.); other marks were paired circular papillae in segments 7 (three ind.), 8 (eight ind.), 9 (two ind.), and 11 (two ind.) and swellings in segments 8 and 9 (three ind.); rarely observed were unpaired (in only one side) papillae in segments 11 and 12; all these marks occluded setae ab. Within the clitellum, paired circular papillae in ab and with a dark center were observed in segments 15 (nine ind.), 16 and 20 (all fifteen individuals) (Fig. 8 A, C); the genital zone that delimits seminal grooves presented in s. 18 small, paired papillae outside seminal furrows (14 ind.) and small swellings or papillae placed lateral or before anterior prostatic pores, or lateral or behind posterior prostatic pores; prostatic pores, in all individuals, delimited by a light circular and small papillae. After clitellum only a midventral, circular and post-setal papillae was observed in s. 21 (eight ind. Fig. 8 C) or 21 / 22 (three ind.). Internal. Septum 5 / 6 very thin and membranous, often not seen; 6 / 7 slightly muscular; 7 / 8 – 12 / 13 muscular; 13 / 14 and afterwards thin, membranous and non- imbricated; 6 / 7 – 9 / 10 funnel shaped and imbricated; 10 / 11 – 12 / 13 slightly imbricated (Fig. 9 A). One round to square gizzard seen in s. 5 (five individuals) or 6 (two ind.), extending in segments 7 – 8 (Fig. 9 A), measuring (length × wide) 1.72 × 1.69 (holotype), 1.65 × 1.7, 1.77 × 1.7 mm. Five pairs of calciferous glands in 9 – 13, those of 9 and 13 being the smaller; they are sessile, kidney shaped (Fig. 9 C); internally each sac with lateral and ventral lamellae with free margins and smaller vessels (Fig. 9 D); externally, with several brown lines which correspond to internal lamellae vascularization (Fig. 9 C). Intestine starts in 15 / 16 (holotype and six paratypes), sacculated in first segments (Fig. 9 A). Typhlosole starting as a small fold in segments 21, 22 (five ind.) (Fig. 9 A) or 17 (one ind.); it gradually increases in size, reaching its maximal dimension four to six segments behind (s. 25 to 28); it is bifid occupying 1 / 4 – 1 / 6 of lumen. It continues with the same shape and size until it abruptly ends 74, 75, 87 or 92 segments before anus. Intestinal caeca absent. Single dorsal vessel visible throughout (Fig. 9 A), easily visible from s. 7. Supra-esophageal vessel observed in 10 – 13; in some individuals gross connections to hearts give the appearance of a double vessel (Fig. 9 C). Lateral hearts seen in 8, 9 and 10; latero-esophageal hearts in 11, 12 and 13 (Fig. 9 C). Paired subesophageal vessels present in 9 – 13; in 14 a pair of ventral vessels anastomose with septa and body wall. A pair of tufted enteronephridia observed in segments 3 (one ind.), 4 (three ind.) or 5 (three ind.) (Fig. 9 B), dorsolateral to pharynx; from each tuft, a duct runs in anterior direction discharging into the mouth. Six dorso-lateral septal meronephridia observed in segments 7 – 11 (three per side), in the anterior face of septa 7 / 8 – 11 / 12. From segment 13 backwards, three parietal, closed meronephridia on each side (6 per segment), in longitudinal rows throughout (Fig. 9 A); after clitellum, they are apparently joined by a thin cord and always closer to the anterior septum. Last segments present a pair of open, median ventral megameronephridia with a clear nephrostome visible in the preceding segment. Holandric. Testes of 10 and 11 ventral, enlarged, attached to anterior septum and joined to male funnels by coagulum. Male funnels iridescent and plicated (in some individuals only enlarged); funnels of 11> 10 (three ind.) or of equal size (five ind.). Male gonoducts double, iridescent, over the body wall, undulating, running outside B and entering body wall in the equator of 17 / 18 (Fig. 10 B). Two pairs of acinous seminal vesicles in 9 and 12 (Fig. 9 A), respectively fixed to septa 9 / 10 and 11 / 12, and lateral to the esophagus; those of 12> 9. Two pairs of tubular prostates of similar size in 17 and 19, coiled with three to five folds and limited to its corresponding segment (Fig. 9 A, 10 A); glandular part larger and wider than muscular duct (Fig. 10 A, B). Connective tissue fibers (retractor muscles) located in some segments of 16 – 21 region and extending from mid-ventral line to lateral walls (Fig. 10 A). Large, paired ovaries on the floor of 13, with a bushy shape and numerous conspicuous eggs; female funnels one pair in 13, at both sides of mid-ventral line. Ovisacs paired in 14, projecting from 13 / 14, lateral to esophagus. Anterior spermathecae one pair in segments 7 (four ind.) or 8 (four ind.), and discharging in 7 / 8; posterior spermathecae one pair in 9, and discharging in 8 / 9; in all cases anterior and posterior spermathecae of similar size and fixed to the wall floor. Ampulla with two clear regions: an ovoidal ental and a straight-narrow ectal (Fig. 10 C). Duct elongated (c. at least one half the length of ampulla), straight or undulating, with an almost sessile or pedunculated spherical diverticulum that come out in the junction to ampullae (Fig. 10 C, D); in almost all observed individuals, diverticulum iridescent and with several seminal chambers. Measures of spermathecae (length per wide in mm): 1.4 × 0.38, 1.26 × 0.35, 1.04 × 0.41, 1.46 × 0.49, 1.55 × 0.42 (average 1.34 × 0.41).	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518207C25FF5FFC6AFC954018.taxon	etymology	Etymology. The name of the species refers to name of the San Martin Volcano in Nahuatl language. Habitat and ecological category. Olmecadrilus titepetlensis sp. nov. was found at the top and in several sites at the base, of the San Martín Volcano. The new species was always found in disturbed to well preserved tropical rain forest; it was also recorded in an elfin forest at the top of the Volcano. It is an endogeic polyhumic species that consumes soil mixed with organic debris. This species was considered as Ramiellona sp. nov. 2 by Fragoso (1997), Ramiellona sp. nov. 15 by Fragoso et al. (2009), and as Ramiellona sp. nov. 17 by Fragoso (2001, 2007).	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518207C25FF5FFC6AFC954018.taxon	discussion	Remarks. Olmecadrilus titepetlensis sp. nov. is clearly separated from all the species of the genus (Table 1) by the posterior widely paired arrangement of setae, where seta d is very close to dorsal pore. In addition, it is separated from all species but O. wilsoni, by the long spermathecal duct; from this last species is separated besides, by owning only one spermathecal diverticulum (vs. two in O. wilsoni).	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518257C2BFF5FFACDFE3D44E0.taxon	description	(Figures 11, 12, 13, 14, 15 C)	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518257C2BFF5FFACDFE3D44E0.taxon	materials_examined	Material Mexico, Veracruz state, Los Tuxtlas Biosphere Reserve (Fig. 15 C): 3) Close to Los Tuxtlas Tropical Biology Station of the UNAM, slightly forward of junction of north boundary marker of the station and the road to Laguna Escondida, municipality of San Andres Tuxtla. Tropical rain forest with abundance of the palm Astrocarium mexicanum, on a slight slope, in the first 10 com of soil depth, 18 ° 35 ' 15.08 " N, 95 ° 04 ' 36.19 " W. 200 m asl, one entire clitellate adult (IEOL- 688) 07 / 16 / 1984, C. Fragoso and P. Lavelle; 4) 2.8 km from the north limit of Los Tuxtlas Tropical Biology Station of the UNAM, on the road to Ruben Sanchez ranch. Ruiz Cortinez forest, property of Silvio Cabañas, municipality of San Andres Tuxtla. Tropical rain forest with Astrocarium mexicanum, over dark, volcanic sandy soils with a deep litter layer, in the first 10 cm of soil depth, 18 ° 36 ' 57.61 " N, 95 ° 05 ' 35.38 " W. 52 m asl, one clitellate adult (IEOL- 218) cut in two pieces 07 / 18 / 1984, C. Fragoso and P. Lavelle, one fragmented clitellate adult (IEOL- 6716) and another cut in two pieces (IEOL- 222) 08 / 12 / 1986, C. Fragoso; 6) Within Los Tuxtlas Tropical Biology Station of the UNAM, 2.7 km after the north boundary and 500 m before the Ruiz Cortinez forest, property of Silvio Cabañas, municipality of San Andres Tuxtla. Tropical rain forest, over dark, sandy soils on a flatland, 18 ° 36 ' 40.51 " N, 95 ° 5 ' 35.52 " W. 90 m asl, two clitellate adults, one entire (IEOL- 201) and one cut in two pieces (IEOL- 206) 10 / 04 / 1986, C. Fragoso; 7) 150 m before the main entrance of Los Tuxtlas Tropical Biology Station of the UNAM, in direction to Sontecompan, municipality of San Andres Tuxtla. Tropical rain forest, Route 1, path 1 of the teaching area of the station. In the first 10 cm of soil depth, 18 ° 35´00.71 " N, 95 ° 04´24.82 " W, 159 m asl, one juvenile with incipient genital marks (IEOL- 4716) 07 / 10 / 2013, J. A. Angeles and M. de los Santos; 9) On the edge of Laguna Escondida, north of Los Tuxtlas Tropical Biology Station of the UNAM, municipality of San Andres Tuxtla. Disturbed tropical rain forest, close to a site with an abundance of orange trees. Along a slope transect from the lake edge, over sandy dark brown stony soils, under stones and in first 10 cm of soil depth, 18 ° 35 ' 31.90 " N, 95 ° 05 ' 14.58 " W. 160 m asl, two fragmented clitellate adults (IEOL- 219, 872) 08 / 11 / 1986, C. Fragoso, anterior fragment of adult with genital marks (IEOL- 221) and one fragmented clitellate adult (IEOL- 192) 04 / 03 / 1986, C. Fragoso; 11) Road Catemaco – Coyame, until reaching the town Miguel Hidalgo y Costilla, continuing 3 km in east direction and then following the crest of the mountain in direction to El Bastonal, municipality of Catemaco. In upper soil and litter, under Liquidambar trees and close to a small stream, cloud forest vegetation. 18 ° 22 ' 40.42 " N, 94 ° 55 ' 23.12 " W, 1075 m asl, two clitellate adults, one entire (IEOL- 200) and one fragmented (IEOL- 208) 04 / 05 / 1986, C. Fragoso and S. Sinaca.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518257C2BFF5FFACDFE3D44E0.taxon	description	External. Length (contracted fixed): 77 – 110 mm (mean ¯ x = 91 mm, n = 6). Width (postclitellar) 3.6 – 6.1 mm (mean = 4.74, n = 7). Segments 220 – 281 (mean = 248, n = 5). Color light grey, without pigment. Prostomium invaginated, prolobic apparently. Secondary furrows one post-setal in segments 4 – 8, from 9 and backwards one pre and one post-setal (Fig. 11 A). Setae eight per segment; ab visible from segment 4, 6 closely paired (Fig. 11 A) and in rows until segment 50, where they start to alternate between segments; setae cd difficult to see before clitellum, after it, they start to alternate (Fig. 11 E); in the posterior region the arrangement clearly quincuaxial (Fig. 11 F). Setae ab of segments 8 and 9 in line with anterior and posterior AB lines, excepting one individual where setae of segment 9 slightly displaces to ML. Clitellum dark reddish, saddle shaped, extending in ½ 13 – 20 (one ind.), ½ 13 – 21 (four ind. Fig. 11 A), ½ 13 – 22 (seven ind.); reaching B or BC lines in the ventral region; intersegmental furrows recognizable in some individuals. Dorsal pores large, present throughout the body; first pore in 11 / 12, from 12 / 13 backwards larger and all the same size (Fig. 11 E). Spermathecal pores small but visible (84, 138 microns): single in midventral line (ML) of 7 / 8 and paired next to ML in 8 / 9 (12 ind.) (Fig. 11 A, C) or paired next to ML in both 7 / 8 and 8 / 9 (three ind.) (Fig. 11 D). Female pores in 14, presetal in A, very small. Seminal grooves mesially concave like parenthesis, in 17 – 19. (Fig. 11 A, B) Two pairs of prostatic pores on the end of seminal grooves, in the middle of 17 and 19 and close to ML (Fig. 11 B). Male pores within the seminal grooves in the equator of 18, minute, and aligned to A or B. Genital marks: swellings in ventral region of segments 8 and 9, or only in 9, in some individuals concentrated in setae ab; c ircular to transversal elliptical paired papillae next to ML and with a darker circular inner center, located in 16 / 17, 17 / 18, 18 / 19 (5 ind.), or 16 / 17, 17 / 18, 18 / 19, 19 / 20 (3 ind., Fig. 11 A), or 15 / 16, 16 / 17, 17 / 18, 18 / 19, 19 / 20, 20 / 21 (1 ind., Fig. 11 B) or 16 / 17, 17 / 18, 18 / 19, 19 / 20, 20 / 21 (1 ind.); tumescences in ML, from b to b, in segments 21 – 30 (1 ind.), 22 – 27 (1 ind.), 22 – 28 (1 ind.), 22 – 32 (1 ind. Fig. 11 B), only seen in four of nine revised clitellate adults. Internal. Septa 5 / 6 – 11 / 12 muscular and funnel shaped, pierced by muscular bands of connective tissue; septa of 12 / 13 and backwards thin and membranous. One large gizzard in 5, preceded by a crop (Fig. 12 A). Six pairs of calciferous glands in 9 – 14 (14 ≤ 13 ≤ 12 = 11> 10> 9), as sessile, ventro-lateral sacs (Fig. 12 B); internally each sac with lateral and ventral lamellae with free margins (Fig. 12 C, D); in some individuals the sacs of 9 and 10 more vascularized. Intestine begins on 16 or 16 / 17. Intestinal typhlosole laminar, starting as a small cord in segment 22, 27, 29 or 30; from these segments it gradually increases in size, until it reaches its larger size in segment 33, 34 or 36. It ends, after gradually diminishing its size, 87, 130 or 160 segments before anus. Intestinal caeca absent. Single dorsal vessel visible throughout (Fig. 12 B), easily visible from s. 7. Supra-esophageal vessel visible in 9 – 13, 14; in segments 11 – 14 it seems to be double apparently due to its join to hearts (Fig. 12 B). Lateral hearts in 6 – 10; latero-esophageal hearts in 11, 12 and 13 (Fig. 12 B). Paired subesophageal vessels in 9 – 13, in the region of calciferous glands (Fig. 12 B); in segment 8 these vessels anastomose to septum 8 / 9. Paired clusters of tufted micronephridia in segment 4, additional smaller tufts attached to the floor are seen in segments 2 and 3; in each side, tufts join a ventral duct that discharges into the mouth in segment 2, just before the pharynx (Fig. 13 A). Lateral septal meronephridia observed in the anterior face of septa 8 / 9 – 11 / 12. A network of parietal nephridia observed in the region of clitellum (Fig. 13 C). Six to seven parietal, closed, meronephridia on each side (12, 14 per segment), seen mainly after the clitellum and backwards (Fig. 13 B). Median ventral meronephridia of last segments larger and with a nephrostome into the preceding segment. Holandric. Testes of 10 and 11 bush shaped, in some individuals joined to the male funnels by coagulum. Male funnels iridescent and plicated, in 10 and 11. Male gonoducts observed in one individual in 14 – 16 close to ML, on the body wall. Two pairs of acinous seminal vesicles in 11 and 12, ventro-lateral to the esophagus and fixed to the corresponding anterior septum: those of 12> 11. Two pairs of tubular prostates of similar size in 17 and 19, limited to its corresponding segment and straight or with a single fold (Fig. 14 A); glandular part two-four times thicker and two-six times larger than muscular duct. Retractor muscles in the clitellar region abundant and as connective tissue fibers, located in segments 16 – 19 (Fig. 14 A). Ovaries one pair on the floor of 13, bushy or fan shaped and with numerous eggs; female funnels one pair in 13. In all dissected individuals, one pair of similar-sized spermathecae discharging in 8 / 9, the position of ampulla varying between individuals: in segment 7 one ind., in s. 8 three ind. and in s. 9 four ind. (Fig. 14 C); ampulla longitudinally elongated, club, sausage and pear shaped with a dorsal and spherical diverticulum which present from one to three seminal chambers (Fig. 14 C). These spermathecae are strongly fixed to the wall floor by connective tissue, being the join of diverticulum and duct intraparietal. A single spermatheca inserts in ML of 7 / 8, with the ampulla in segment 7 (two ind.) or s. 8 (three ind. Fig. 14 B); in all cases with two lateral and spherical diverticula. Anterior spermatheca strongly fixed to wall floor. A variation, however, was observed in two individuals that presented two ampullae discharging in 7 / 8. In the first individual the two ampullae discharge through a common duct in ML (Fig. 14 D), each one with its own diverticulum; in the second individual the two ampulla discharge through its own duct, lateral to ML, each one with its own diverticulum.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518257C2BFF5FFACDFE3D44E0.taxon	biology_ecology	Habitat and ecological category. By the lack of pigmentation, slow movements and intestinal content mainly composed of mineral soil, the individuals of O. mexicanus from Los Tuxtlas are the typical endogeic worms. They were found mainly in undisturbed tropical rain forests, with some records in disturbed tropical forests and cloud forests.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
03F14C5518257C2BFF5FFACDFE3D44E0.taxon	discussion	Remarks: In general, the morphology of Los Tuxtlas worms of O. mexicanus is very similar to the original description from Dos Ríos (Gates, 1962). There are, however, some characters differing between both descriptions. Gates (1962) did not see sessile sacs in the region of segments 9 – 14, although he clearly stated an “ Esophagus deeply constricted at the septal insertions and markedly moniliform through ix-xiv … and … narrow ”; on the other hand he recognized (supposedly in all these segments, as it is inferred from the text) the same morphology of the calciferous lamellae observed in Los Tuxtlas material: lamellae attached to the floor and lateral walls, and with free median and dorsal margins. Another difference is in the type of prostatic glands, which are coiled in the worms from Dos Ríos, and without folds or with a single one, in the material from Los Tuxtlas. Finally, the variation observed in Los Tuxtlas worms about the amount of spermathecae that discharge in 7 / 8 is remarkable: one spermatheca with two diverticula, two spermathecae each one with one diverticulum, and two ampullae sharing the same duct, each ampulla with its own diverticulum. Accordingly, we consider that differences observed within Los Tuxtlas populations and between Los Tuxtlas sites and Dos Ríos correspond, respectively, to within and between species geographical variation.	en	Fragoso, Carlos, Rojas, Patricia (2026): Olmecadrilus gen. nov. (Annelida, Crassiclitellata), a new acanthodrilid meroic earthworm genus from eastern Mexico including the description of three new species. Zootaxa 5750 (4): 451-481, DOI: 10.11646/zootaxa.5750.4.1, URL: https://doi.org/10.11646/zootaxa.5750.4.1
