taxonID	type	description	language	source
CF6B87F3E6388511FF6FFA99FD3EFE3C.taxon	description	Figures 3 Zoobank registration. urn: lsid: zoobank. org: act: A 12 B 4 C 50 - 5 E 92 - 4 CDF-B 49 D- 748479 A 4 DE 01	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6388511FF6FFA99FD3EFE3C.taxon	materials_examined	Materials examined. Digital video and photographs of original living specimen, Holotype (SMNH Type- 9424) Type locality. Cala Stagno Lungo, Asinara Island, Italy, 41 ° 03 ’ 53 N, 8 ° 17 ’ 03 E Habitat. 0.3 – 1 m depth, marine, medium sand.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6388511FF6FFA99FD3EFE3C.taxon	diagnosis	Diagnosis. Body length 0.4 – 0.6 mm. Body clear and without pigmentation. Frontal organ small. Rhabdoid glands in longitudinal rows. Posterior vacuole present. Paired testes and ovaries. Seminal bursa present just posterior to largest egg. Male copulatory organ large, with penis partially invaginated into the seminal vesicle. Penis 17 – 20 µm long, curved. Antrum masculinum small, ciliated. Male gonopore subterminal.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6388511FF6FFA99FD3EFE3C.taxon	etymology	Etymology. This species is named for its type locality, Asinara Island.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6388511FF6FFA99FD3EFE3C.taxon	description	Description. Living specimen 0.45 – 0.60 mm long and to 0.12 mm width at midpoint. Free-swimming specimens lively and quick. Elongate with rounded anterior and posterior ends. Body colorless, without pigmentation and clear. Numerous lipid droplets of varying sizes present in digestive parenchyma and throughout the body, clear to yellow in color. Digestive parenchyma extends from just posterior of statocyst to level of posterior egg. Mouth not observed. Frontal organ small, just reaching level of statocyst. Statocyst present 70 µm from anterior end, 10 – 12 µm in diameter with 6 – 7 µm statolith. Posterior vacuole present. Epidermis completely ciliated. Cilia 4 – 6 µm long. Rhabdoid glands clearly distributed in longitudinal rows. Rhabdoid glands partially subepidermal, colorless, 6 µm in length. Ovaries and testes paired. Small seminal bursa present, located just below largest egg and typically with sperm. Bursa indistinct without walls or ornamentation, globular, 26 – 30 µm long and 16 – 18 µm wide. Separate female gonopore present at ventral midline ~ 70 µm from posterior end of animal. Male copulatory organ large, 39 – 40 µm long and 36 – 36 µm wide. Globular. Penis invaginated into the seminal vesicle and extending into the antrum masculinum. Isodiametric penis curved, 17 – 20 µm long. Antrum masculinum short, ciliated. Male gonopore at ventral midline.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E63C851EFF6FFDA8FF76FC95.taxon	description	Figure 4 Zoobank registration. urn: lsid: zoobank. org: act: 7464785 C- 58 B 6 - 499 C-BDCA-BEF 48 B 373812	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E63C851EFF6FFDA8FF76FC95.taxon	materials_examined	Materials examined. Digital video and photographs of original living specimen, Holotype (SMNH Type- 9425) Type locality. Saltö Badstrand, Strömstad, Sweden; 58 ° 52 ’ 41 N, 11 ° 06 ’ 56 E Habitat. 2 m depth, marine, medium sand	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E63C851EFF6FFDA8FF76FC95.taxon	diagnosis	Diagnosis. Body length 0.85 mm. Body pigmentation absent. Frontal organ small. Rhabdoid glands distributed in longitudinal rows. Vacuoles absent. Paired testes and ovaries. Seminal bursa absent. Male copulatory organ with penis partially invaginated into the seminal bursa. Penis 27 µm long, curved. Male gonopore subterminal.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E63C851EFF6FFDA8FF76FC95.taxon	etymology	Etymology. This species is named for its type locality, Saltö (Latin: sal salt; insula island)	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E63C851EFF6FFDA8FF76FC95.taxon	description	Description. Living specimen 0.85 mm long and to 0.18 mm maximum width. Free-swimming specimens elongate with rounded anterior end and pointed posterior. Body colorless, except for parenchyma, which is dark yellow or brown from food. Numerous lipid droplets of varying sizes present in digestive parenchyma and throughout the body, clear to yellow in color. Digestive parenchyma extends from just posterior of statocyst to posterior eggs. Mouth not observed. Frontal organ small, not extending to level of statocyst. Statocyst present 115 µm from anterior end, 15 µm in diameter with 11 µm statolith. Vacuoles absent. Epidermis completely ciliated. Cilia 6 – 7 µm long. Rhabdoid glands distributed in longitudinal rows. Posterior rhabdoid glands partially subepidermal, colorless, 8 – 10 µm in length. Ovaries and testes paired. Ovaries anterior to male copulatory organ, present in the posterior ~ ¼ of the animal. Seminal bursa absent. Vagina and female gonopore not observed. Male copulatory organ close to posterior end, globular with a width of 56 µm and a length of 52 µm. Penis partially invaginated into seminal vesicle. Penis small, 27 µm long, and curved. Male gonopore located at ventral midline.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E633851EFF6FFC4DFE3EF83C.taxon	description	Figure 5 Zoobank registration. urn: lsid: zoobank. org: act: 69575 F 0 F-E 9 FA- 412 E-B 902 - F 9 D 0 E 77 C 584 D	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E633851EFF6FFC4DFE3EF83C.taxon	materials_examined	Materials examined. Digital video and photographs of original living specimens, Holotype (SMNH Type- 9426) and Paratypes (SMNH Type- 9427 – SMNH Type- 9431) Type locality. Saltö Badstrand, Strömstad, Sweden; 58 ° 52 ’ 41 N, 11 ° 06 ’ 56 E Habitat. 0.5 – 1 m depth, marine, medium sand	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E633851EFF6FFC4DFE3EF83C.taxon	diagnosis	Diagnosis. Body length 0.5 – 0.7 mm. Body colorless, without pigmentation. Frontal organ large. Rhabdoid glands sparsely distributed in longitudinal rows. Vacuoles absent. Paired testes, unpaired ovary. Seminal bursa present without ornamentation. Gonopores separate. Male copulatory organ with penis partially invaginated into the seminal vesicle. Penis 45 µm long, curved. Antrum masculinum unciliated. Male gonopore at ventral midline.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E633851EFF6FFC4DFE3EF83C.taxon	etymology	Etymology. This species is named in reference to the small, curved penis that is the prevailing morphological character distinguishing it from B. macrospiriferum	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E633851EFF6FFC4DFE3EF83C.taxon	description	Description. Living specimen 0.5 – 0.7 mm in total body length and to 0.13 mm maximum width. Specimens in squeeze-preparation drop-shaped; free-swimming specimens more elongate with rounded anterior and posterior ends. Body colorless, transparent, except for parenchyma, which varies from green or yellowish-brown based on microalgae food. Lipid globules few, mostly smaller in size than statocyst. Mouth located approximately ¼ of the way from the anterior end. Digestive parenchyma extending from mouth to level of the largest, posteriormost egg. Mouth present at approximately ⅓ body length from the anterior end. Frontal organ large, extending posterior to statocyst. Statocyst present 70 – 80 µm from anterior end, 17 – 18 µm in diameter with 11 – 12 µm statolith. Epidermis completely ciliated and ~ 4 µm wide in longitudinal sections. Cilia 4 – 6 µm long. Rhabdoid glands relatively sparse, distributed in longitudinal rows. Posterior rhabdoid glands partially subepidermal, colorless, 9 µm in length. Ovary unpaired. Seminal bursa present just posterior to largest egg. Bursa elongate with evident sperm bundle. Bursa without distinct walls, approximately 30 – 35 µm long and to 45 µm (34 – 45) wide. Bursal nozzles and appendages absent. Short, unciliated vagina leading to separate female gonopore. Testes paired, located just anterior of the midbody. Male copulatory organ terminal in posterior end, spherical or globular with a width of 48 – 51 µm and a length of 44 – 45 µm. Penis partially invaginated into seminal vesicle, extending outward into the unciliated antrum masculinum. Penis slightly curved, 44 – 45 µm long. Male gonopore located at ventral midline.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E632851AFF6FF9F0FDE9FE93.taxon	description	Figure 6, 7 Zoobank registration. urn: lsid: zoobank. org: act: 85 B 18597 - A 6 A 7 - 4135 - A 0 A 3 - 10 D 2 C 7 C 9 EC 5 E	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E632851AFF6FF9F0FDE9FE93.taxon	materials_examined	Materials examined. Serial sectioned specimen, Holotype (SMNH Type- 9432); Digital video and photographs of original living specimens and serial sectioned specimens, Paratypes (SMNH Type- 9433 – SMNH Type- 9452) Type locality. Vale de Covo, Carvoeiro, Portugal, 37 ° 05 ’ 33.4 N 8 ° 27 ’ 34.9 W Habitat. 1 m depth, marine, fine sand	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E632851AFF6FF9F0FDE9FE93.taxon	diagnosis	Diagnosis. Body length 0.5 mm. Body clear and without pigmentation. Frontal organ large. Rhabdoid glands numerous in clear longitudinal rows. Posterior vacuole present. Paired testes and unpaired ovary. Seminal bursa without distinct walls present with small, arched bursal nozzle. Male copulatory organ large, with penis partially invaginated into the seminal vesicle. Penis 30 – 40 µm long, sharply curved. Antrum masculinum large, unciliated. Male gonopore ventral.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E632851AFF6FF9F0FDE9FE93.taxon	etymology	Etymology. This species is named in reference to the arched shape of the bursal nozzle (Latin: arcuatum arched).	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E632851AFF6FF9F0FDE9FE93.taxon	description	Description. Living specimen 0.5 mm long and to 0.09 mm at widest point. Animal broadest in the anterior at level of statocyst, width tapering towards the posterior. Anterior and posterior ends rounded. Body colorless, without pigmentation and clear. Numerous lipid droplets of varying sizes present in digestive parenchyma and throughout the body, clear to yellow in color. Digestive parenchyma extends from ~ ¼ body length from the anterior to level of the most posterior egg. Mouth present just anterior to midbody. Frontal organ large, extending past level of statocyst. Statocyst present 65 µm from anterior end, 10 – 11 µm in diameter with 6 µm statolith. Posterior vacuole present. Epidermis completely ciliated. Cilia 4 – 6 µm long. Rhabdoid glands numerous, distinctly distributed in longitudinal rows. Rhabdoid glands partially subepidermal, colorless, 6 µm in length. Ovary unpaired, often with numerous large eggs. Seminal bursa present with bursal nozzle. Bursa without distinct walls, ~ 45 µm long, typically with sperm present in the anterior near the nozzle. Bursal nozzle 7 – 8 µm wide, arching with thin lateral extensions. Vagina and female gonopore not observed. Testes paired, located ¼ body length from the anterior. Male copulatory organ large, 37 – 39 µm long and 42 – 44 µm wide. Globular. Penis partially invaginated into the seminal vesicle, with the tip extending into a large antrum masculinum. Penis sharply curved, “ J ” shaped, 30 – 40 µm long. Proximal end of penis surrounded by the prostatic vesicle. Antrum masculinum unciliated. Male gonopore ventral. Genus Praeaphanostoma DÖRJES 1968	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E637851BFF6FFE6CFAB3FC24.taxon	description	Figure 8 Zoobank registration. urn: lsid: zoobank. org: act: 091 F 3968 - 6642 - 44 CD- 9799 - 37 A 65 EFB 701 C	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E637851BFF6FFE6CFAB3FC24.taxon	materials_examined	Materials examined. Serial sectioned specimen, Holotype (SMNH Type- 9453); Digital video and photographs of original living specimens and serial sectioned specimens, Paratypes (SMNH Type- 9454 – SMNH Type- 9467). Type locality. Klubban beach, Gullmarsfjorden, Sweden, 58 ° 15 ’ 05 N, 11 ° 27 ’ 52 E; Kvarnbukten, Bohuslän, Sweden, 58 ° 15 ’ 31 N, 11 ° 28 ’ 28 E Habitat. 1 – 2.5 m depth, marine, silty sand with organic content; 1 – 1.5 m depth, medium sand	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E637851BFF6FFE6CFAB3FC24.taxon	diagnosis	Diagnosis. Body length 0.5 – 0.9 mm. Body pigmentation absent. Frontal organ moderate in size. Rhabdoid glands sparse in rows. Vacuoles absent. Testes paired; ovary unpaired. Seminal bursa present without ornamentation. Short vagina connects to common antrum and gonopore. Male copulatory organ subterminal without penis.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E637851BFF6FFE6CFAB3FC24.taxon	etymology	Etymology. This species is named in reference to the numerous diatoms present in the digestive parenchyma of the type specimens.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E637851BFF6FFE6CFAB3FC24.taxon	description	Description. Living specimen 0.5 – 0.9 mm in total body length depending on state of elongation and 0.12 – 0.2 mm in maximum width at point of largest egg. Specimens in squeeze-preparation drop-shaped; free-swimming specimens more elongate with rounded anterior and posterior ends. Body colorless, transparent, except for parenchyma, which varies from green or yellowish-brown based on microalgae food. Digestive parenchyma extends from ¼ body length from the anterior to level of posterior egg. Mouth present just past ¼ body length from anterior end, ~ 22 µm in width. Frontal organ extending from anterior end to just posterior to statocyst. Statocyst present 90 – 110 µm from anterior end, 11 µm in diameter with 8 µm in diameter statolith. Epidermis completely ciliated and ~ 4 µm wide in longitudinal sections. Cilia 4 – 6 µm long. Rhabdoid glands present in longitudinal rows, sparse and best visible at the posterior end. Posterior rhabdoids partially subepidermal, colorless, 9 – 10 µm in length. Ovary unpaired with up to four eggs. Seminal bursa present just posterior to largest egg. Bursa globular or eggshaped with narrower, tapering proximal part; width to 36 µm (24 – 36 µm) and length to 65 µm (46 – 65 µm). Bursa typically filled with evident sperm. Bursal nozzles or appendages absent. A short unciliated vagina connects the bursa ventrally to a common antrum and gonopore. Testes paired, located just posterior of the midbody and anterio-lateral to the ovary. Seminal vesicle subterminal in posterior end, spherical or globular with a width of 23 – 38 µm and a length of 25 – 38 µm. Penis absent.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6368518FF6FFBDDFDCCF943.taxon	description	Figure 9 Zoobank registration. urn: lsid: zoobank. org: act: 010 B 5 C 0 C- 78 D 2 - 4 EF 4 - 975 D-F 8 D 990526 E 8 B	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6368518FF6FFBDDFDCCF943.taxon	materials_examined	Materials examined. Digital video and photographs of original living specimen, Holotype (SMNH Type- 9468). Type locality. North of Ellenbogen, Sylt, Germany; 55 ° 03 ’ 13 N, 8 ° 27 ’ 24 E Habitat. 16 m depth, marine, medium sand	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6368518FF6FFBDDFDCCF943.taxon	diagnosis	Diagnosis. Animal short and wide, 0.6 mm body length and 0.23 mm width. Frontal organ small. Rhabdoid glands highly abundant in longitudinal rows. Unpaired ovary. Bursa present, simple without adornment. Male copulatory organ subterminal with evident small penis. Penis conical, 12 µm long. Vacuoles absent.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6368518FF6FFBDDFDCCF943.taxon	etymology	Etymology: This species is named in reference to the more than ten years length of time between specimen collection and species description (Latin: neglectus neglected)	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6368518FF6FFBDDFDCCF943.taxon	description	Description. Living specimen 0.60 – 0.65 mm in total body length and 0.23 mm at the midpoint. Body shape elliptical with bluntly rounded anterior end and rounded posterior end. Body colorless, transparent, except for brown-orange parenchyma from food. Mouth located approximately ⅓ of the way from the anterior end. Digestive parenchyma extending to level of posterior egg. Frontal organ small, extending from the anterior end halfway to the statocyst. Statocyst present 125 µm from anterior end, 20 µm in diameter with 15 µm statolith. Epidermis uniformly ciliated. Cilia 8 – 10 µm long. Rhabdoid glands highly abundant in longitudinal rows, partially subepidermal across body, colorless, 6 – 9 µm in length. Ovary unpaired, with up to four eggs. Seminal bursa present just posterior to largest egg. Bursa elliptical with allosperm generally present in the anterior portion. Bursa width to 67 µm and length to 36 µm. Bursal nozzles or appendages absent. Female gonopore and vagina not observed. Testes paired, located midbody and just anterior to the ovary. Male copulatory organ subterminal in posterior end, roughly globular with a diameter of 48 – 50 µm. Penis invaginated into seminal vesicle and extending caudally, straight and gently conical. Penis length 12 µm, conical, width at the base 12 µm and at the tip 3 µm. Male gonopore present. Genus Pseudoposthia WESTBLAD 1946	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6358506FF6FF956FB91FC6C.taxon	description	Figure 10 Zoobank registration. urn: lsid: zoobank. org: act: 70 BAF 94 F-C 846 - 4156 - 84 FD- 70 B 58301213 A	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6358506FF6FF956FB91FC6C.taxon	materials_examined	Materials examined. Serial sectioned specimen, Holotype (SMNH Type- 9469); Digital video and photographs of original living specimens, Paratypes (SMNH Type- 9470 – SMNH Type- 9480) Type locality. Getryggen, Skaggerak, Sweden, 58 ° 34 ’ 18 N, 11 ° 13 ’ 14 E; Vedholmen-Hamnholmen, Skaggerak, Sweden, 58 ° 33 ’ 44 N, 11 ° 11 ’ 30 E; Vrakholmen, Skaggerak, Sweden, 58 ° 35 ’ 06 N, 11 ° 12 ’ 05 E; Basteviken, Skaggerak, Sweden, 58 ° 53 ’ 52 N, 10 ° 59 ’ 24 E. Habitat. 6 – 10 m depth, medium to coarse sand with silt	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6358506FF6FF956FB91FC6C.taxon	diagnosis	Diagnosis. Animal small and wide, 0.35 – 0.5 mm long and to 0.25 mm wide. Numerous large rhabdoid glands scattered across body. Vacuoles restricted to the posterior end. Ovaries and testes paired. Bursa absent. Unwalled false seminal vesicle leading to paired false seminal vesicles and paired testes. Male system located ventral to the ovaries and anterior to the largest egg. Gonopore large and distinct, surrounded by muscular sphincter. Penis absent.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6358506FF6FF956FB91FC6C.taxon	etymology	Etymology. This species is named in reference to the broad width relative to the length of the animal (Latin: lata broad)	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6358506FF6FF956FB91FC6C.taxon	description	Description. Animal short and wide, body length 0.35 – 0.5 mm and width to 0.25 mm. Specimens in squeezepreparation drop-shaped with rounded ends. Anterior or midpoint broader relative to the posterior. Body colorless, transparent, except for parenchyma, which varies from bright green or yellowish-brown based on microalgae food. Mouth present approximately at body’s midpoint Frontal organ moderate, extending from anterior end to just posterior to statocyst. Statocyst present 65 µm from anterior end, 15 µm in diameter with 12 µm in diameter statolith. Epidermis completely ciliated and ~ 5 µm wide in longitudinal sections. Cilia ~ 6 µm long. Rhabdoid glands large, numerous and scattered across the body. Rhabdoids partially subepidermal, to 22 µm in length in living specimen. Paired ovaries with numerous eggs. Largest egg medial near the caudal end, just anterior to the posterior vacuoles. Seminal bursa, vagina and female gonopore absent. Male system present anterior of the largest egg. Central false seminal vesicle globular, to 45 µm (38 – 45 µm) in width, connecting laterally to paired false seminal vesicles and testes. False seminal vesicles lack walls and are non-muscular, comprising of a mass of sperm or possibly spermatophore. Testes located ~ ⅓ body length from the anterior end. Large and distinct gonopore present just anterior to the central false seminal vesicle, 34 – 35 µm wide and 18 – 20 µm long. Gonopore surrounded by muscular sphincter. Penis absent.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E62B8504FF6FFBE0FE48FE40.taxon	description	Figure 11 Zoobank registration. urn: lsid: zoobank. org: act: 0 E 41935 C-E 677 - 427 A-BA 6 C-EB 5683043453	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E62B8504FF6FFBE0FE48FE40.taxon	materials_examined	Materials examined. Digital video and photographs of original living specimens, Holotype (SMNH Type- 9481) and Paratype (SMNH Type- 9482). Type locality. Väderöarna naturhamn, Skagerrak, Sweden, 58 ° 34 ’ 52 N, 11 ° 03 ’ 52 E Habitat. 4 – 6 m depth, coarse sand and rocks with some shell hash	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E62B8504FF6FFBE0FE48FE40.taxon	diagnosis	Diagnosis. Body length 0.45 mm long and to 0.15 mm wide in squeezed preparation. Frontal organ well-developed. Rhabdoid glands numerous and scattered. Several large vacuoles present in posterior half of the body. Ovaries and testes paired. Bursa absent. Unwalled false seminal vesicle located ventral to the ovaries and anterior to the largest egg, leading directly to the gonopore posterior to the penis. Glandular penis straight, 9 – 10 µm long. Gonopore large and distinct, surrounded by thick muscular sphincter.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E62B8504FF6FFBE0FE48FE40.taxon	etymology	Etymology. This species is named in honor of the late Dr. Hans G. Hansson, expert in North Atlantic marine fauna and long-time staff member at Tjärnö marina laboratorium.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E62B8504FF6FFBE0FE48FE40.taxon	description	Description. Animal short and wide, body length 0.45 mm and width to 0.15 mm in squeeze-preparation. Specimens widest at midbody with broadly rounded anterior end and pointed rounded posterior end. Body colorless, transparent, except for parenchyma, which varies from bright green or yellowish-brown based on microalgae food. Digestive parenchyma extends from first ¼ body length to just anterior of posterior vacuoles. Mouth present just anterior to body’s midpoint. Several vacuoles present laterally in posterior half of the body. Frontal organ well-developed. Statocyst present 50 µm from anterior end, 11 – 12 µm in diameter with 7 - 8 µm in diameter statolith. Epidermis completely ciliated and ~ 5 µm wide in longitudinal sections. Cilia ~ 6 – 8 µm long. Rhabdoid glands numerous and scattered across the body. Rhabdoids partially subepidermal, 8 – 10 µm in length in living specimen. Paired ovaries with numerous eggs. Largest egg medial and slightly posterior to midpoint. Seminal bursa and female gonopore absent. Seminal vesicle present ventral to the ovaries and anterior of the largest egg. False seminal vesicle globular, 22 – 25 µm in width and to 40 µm long (25 – 40 µm), extending anterio-laterally to testes. Testes located ~ ⅓ body length from the anterior end. Gonopore large and distinct, present at midbody, surrounded by a large muscular sphincter. Gonopore 25 µm wide and 12 – 14 µm long. Small, lightly muscular penis present, 9 – 10 µm long, straight, connecting directly to the gonopore. Penis highly glandular. Two lateral false seminal vesicles connect to a central false seminal vesicle. False seminal vesicles lack walls and are non-muscular, comprising of a mass of sperm or possibly spermatophore. As typical for the genus (Westblad 1946), the central false seminal vesicle is unconnected to the penis, instead remaining posterior to the penis and directly opening into the gonopore (Figure 11 D).	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6298505FF6FFDCCFA1EFADA.taxon	description	Soon after its establishment, the three species comprising Baltalimania ax 1959 were split into two genera based on the presence or absence of bursal tissue (Dörjes 1968). Archaphanostoma DöRJES 1968 was erected for those species that possessed an indistinct bursa without a muscular wall (i. e. bursal tissue) while the bursa-less Baltalimania kosswigi DöRJES 1968 remained in a monotypic genus. Following a phylogenetic analysis of nucleotide sequences from three genes that resulted in species with and without bursas nesting together in a single clade, Atherton & Jondelius (2021) synonymized Archaphanostoma and Baltalimania such that Baltalimania comprised a set of nine species, four with and five without bursal tissue. With the addition of the four new species presented here, the results from our phylogenetic analyses reinforces the close relationships of species of Baltalimania with and without bursal tissue, and indicates that bursal tissue within Baltalimania was independently lost in at least two separate evolutionary lines (Figure 1). Our results are thus in accordance with the conclusions of previous studies (Jondelius et al. 2011; Atherton & Jondelius 2021) that found bursal tissue is not a good character with which to differentiate genera of Isodiametridae. Of note, B. arcuatum sp. nov. is only the second species of Baltalimania to possess a bursal nozzle, the other being B. marcusi (HooGE = & = RocHa 2006). Unlike B. marcusi, the nozzle of B. arcuatum appears as a single unit instead of of multiple disparate components that in theory function together along a single spermatic duct through which sperm pass on the way to the ovary (Petrov et al. 2006; Hooge & Tyler 2003). As no DNA sequences are currently available for B. marcusi, it is not possible at this time to assess the homology of the nozzles by molecular phylogenetics, but the complete absence of bursal tissue as well as the presence of several different bursal types (e. g. indistinct without walls and unadorned, indistinct with a nozzle of a single unit, or indistinct with a nozzle of multiple disjoint units) within closely related species makes Baltalimania a particularly interesting candidate for future studies on bursal development. Further, as the bursa receives allosperm, there is potential for coevolution between it, the male copulatory organ, and sperm morphology among isodiametrids. Overall, the four new species of Baltalimania fit well with the other species of the genus, which are characterized primarily by the presence of a large, muscular seminal vesicle as well as by a bursa that is either absent or present but indistinct and without discernable walls. They also all have numerous lipid globules and rhabdoid glands in distinct longitudinal rows. The previous and new species of Baltalimania can all be relatively easily distinguished from each other based on a few morphological characters, summarized in Table 2 as well as Table 1 of Kånneby et al. (2014).	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6288502FF6FFAACFA1EF962.taxon	description	P. diatomovorum sp. nov. joins P. schillingi (HooGE = & = TYLER 2015) as the second Praeaphanostoma without a penis, a morphology that is incongruous with the proposed diagnostic character of Isodiametridae: a tubular isodiametric penis with inner circular muscles fibres and outer non-anastomosing longitudinal fibres (Hooge & Tyler 2005). Hooge & Tyler (2015) originally described P. schillingi as a species of Haplogonaria DöRJES 1968 because of this discrepancy and assumed the molecular data was due to error. Atherton & Jondelius (2021) later reassigned the species to Praeaphanostoma based on results from their phylogenetic analyses as well as the morphological similarities between P. schillingi and P. rubrum DöRJES = 1968. With P. diatomovorum sp. nov., our results strengthen the inclusion of P. schilingi in the genus and suggest that an isodiametric penis should not necessarily be a diagnostic feature of the genus or family. Unfortunately, without the definitive presence of a penis, the generic diagnosis of Praeaphanostoma does overlap with the generic diagnosis of Haplogonaria. Since no sequence data is available for any species of Haplogonaria, current phylogenetic analyses cannot clarify the situation. Representation of Haplogonaria in a comprehensive phylogenetic analysis must be prioritized in the future to establish the relationships between species of Haplogonaria and Praeaphanostoma and to help uncover apomorphic characters for the two genera.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E6288502FF6FFAACFA1EF962.taxon	diagnosis	P. diatomovorum sp. nov. can be easily distinguished from P. schillingi by the smaller body size and by the lack of bright red body pigmentation. Further, P. diatomovorum sp. nov. can be distinguished from the majority of species of Haplogonaria by its general body shape and size as well as the moderate size of the frontal organ. Finally, it differs from H. minima (WESTbLaD 1946) and H. psammalia FaubEL 1974 by the amount of rhabdoid glands (sparse vs numerous), the size of the bursa (~ 65 µm in length vs 100 – 150 µm) and the lack of a bursal cap; and from H. arenaria (ax 1959) by its less well-developed testes, the presence of a short vagina and the absence of vacuoles. Praeaphanostoma neglectum sp. nov. possesses many typical features of the genus: a walled seminal bursa without appendages, a muscular seminal vesicle with an embedded penis and a small frontal organ. However, it is distinguished from the other species by the combination of an unpaired ovary, an absence of vacuoles, and a body length less than 1 mm.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E62F8503FF6FF934FC2DFB87.taxon	description	Only a single species of Pseudoposthia, P. macrogonopora, was previously known, and its reproductive system notably also does not follow that which is typical of Isodiametridae. In this case, P. macrogonopora does not possess a muscular seminal vesicle with an invaginated isodiametric penis but rather a false seminal vesicle unconnected to the muscular penis (Westblad 1946). Its reproductive system is additionally unusual for Acoela in that the seminal vesicle is not fully posterior to the ovaries. Sequences of P. macrogonopora are presented here for the first time as well as two additional new species of Pseudoposthia. Results from our phylogenetic analyses find the clade does nest within Isodiametridae with high support (Figure 1). The reproductive systems of both new species are similar to that of P. macrogonopora, both in the anterior position of the male system, the false seminal vesicle unconnected to a penis and the lack of female accessory organs. Additionally, all three species are unpigmented and possess numerous rhabdoid glands scattered across the body. P. hanssoni sp. nov. can be differentiated from P. macrogonopora by its smaller body size, a smaller sized penis that is also straight, and by the large vacuoles that are restricted to the posterior body half only. P. lata sp. nov. can be distinguished from P. macrogonopora and P. hanssoni sp. nov. in its general body shape, the medium size of the frontal organs and by the fact that the muscular penis is absent. Table 3 summarizes the primary morphological differences between the three species.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
CF6B87F3E62F8503FF6FF934FC2DFB87.taxon	diagnosis	Emended diagnosis. Body without pigmentation. Frontal organ present, often well-developed. Rhabdoid glands numerous, scattered. Mouth ventral, located approximately at the body’s midpoint and slightly anterior to the male gonopore. Ovaries and testes paired. Seminal bursa, vagina and female gonopore absent. Male reproductive system and gonopore present anterior to the posteriormost portion of the ovary. Male gonopore ventral, surrounded by a heavy muscular sphincter. Penis, when present, without ejactulatory duct and unconnected to a seminal vesicle. False seminal vesicle without walls or musculature present, connecting directly to the gonopore posterior to the penis. Numerous gland cells associated with penis and male gonopore.	en	Atherton, Sarah, Jondelius, Ulf (2022): Diversity in the family Isodiametridae (Acoela): New species bring back old problems. Zootaxa 5169 (5): 401-424, DOI: https://doi.org/10.11646/zootaxa.5169.5.1
