Table 1. Record of abnormal Silurian trilobites.
Ordered by stage and then genus.
| Taxon | Family | Series | Stage | Formation, country | Abnormality location | Abnormality description | Side | Citation and figure |
|---|---|---|---|---|---|---|---|---|
| Acernaspis elliptifrons (Esmark, 1833) | Lichidae | Llandovery | Aeronian | Solvik Formation, Sweden | Pygidium | Asymmetrically developed furrows | Both | Owen (1985, fig. 5t) |
| Encrinurus squarrosus Howells, 1982 | Encrinuridae | Llandovery | Aeronian | Newlands Formation, Scotland | Pygidium | Damaged rib | Right | Howells (1982, pl. 8, fig. 12) |
| Encrinurus squarrosus | Encrinuridae | Llandovery | Aeronian | Newlands Formation, Scotland | Pygidium | Bifurcating rib | Right | Howells (1982, pl. 8, fig. 13) |
| Coronocephalus sp. | Encrinuridae | Llandovery | Telychian | Fentou Formation, China | Pygidium | Deformed, fused pygidial ribs | Right | Zong (2021, fig. 4D, E) |
| Coronocephalus sp. | Encrinuridae | Llandovery | Telychian | Fentou Formation, China | Pygidium | Truncated pygidial ribs | Right | Zong et al. (2017, fig. 3q); Zong 2021, fig. 4F, G) |
| Coronocephalus sp. | Encrinuridae | Llandovery | Telychian | Fentou Formation, China | Pygidium | Additional pygidial rib | Right | Zong (2021, fig. 4H, I) |
| Kailia intersulcata (Chang, 1974) | Encrinuridae | Llandovery | Telychian | Fentou Formation, China | Thorax | Thoracic spines 2–5 truncated, U-shaped indentation | Right | Zong (2021, fig. 4A–C) |
| Odontopleura (Sinespinaspis) markhami | Odontopleuridae | Llandovery | Telychian | Cotton Formation, NSW, Australia | Thorax | Additional thoracic spine base | Right | This article, Figs. 3A and 3B |
| Odontopleura (Sinespinaspis) markhami | Odontopleuridae | Llandovery | Telychian | Cotton Formation, NSW, Australia | Thorax | Additional spine base and offset spine base | Right | This article, Figs. 3C and 3D |
| Odontopleura (Sinespinaspis) markhami | Odontopleuridae | Llandovery | Telychian | Cotton Formation, NSW, Australia | Thorax | Additional posterior pleural band spine bases | Right | This article, Figs. 4A and 4B |
| Odontopleura (Sinespinaspis) markhami | Odontopleuridae | Llandovery | Telychian | Cotton Formation, NSW, Australia | Thorax | Additional thoracic spine base | Right | This article Figs. 4C and 4D |
| Odontopleura (Sinespinaspis) markhami | Odontopleuridae | Llandovery | Telychian | Cotton Formation, NSW, Australia | Thorax | Additional thoracic spine base | Right | This article, Figs. 4E and 4F |
| Odontopleura (Sinespinaspis) markhami | Odontopleuridae | Llandovery | Telychian | Cotton Formation, NSW, Australia | Thorax | Additional thoracic spine base | Right | This article, Figs. 5A and 5B |
| Odontopleura (Sinespinaspis) markhami | Odontopleuridae | Llandovery | Telychian | Cotton Formation, NSW, Australia | Thorax | Additional posterior pleural band spine bases | Left | This article, Figs. 5C and 5D |
| Decoroproetus corycoeus (Conrad, 1842) | Proetidae | Wenlock | Sheinwoodian- Homerian | St. Clair Formation, Arkansas, USA | Thorax, pygidium | Thoracic segment 11? fused to pygidium | Right | Holloway (1980, pl. 3, fig. 4) |
| Calymene frontosa Lindström, 1885 | Calymenidae | Wenlock | ?Sheinwoodian | Visby Beds, Sweden | Cephalon | Abnormal development of suture | Left | Owen (1985, fig. 5c) |
| Arctinurus boltoni (Bigsby, 1825) | Lichidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Pygidium | Truncated posteriormost pygidial spine, ‘W’-shaped injury | Right | Rudkin (1985, fig. 1A, B) |
| Arctinurus boltoni | Lichidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Thorax, pygidium | Large ‘U’-shaped indentation, posterior thorax, extending onto pygidium | Right | Babcock (1993b, p. 36, no figure number) |
| Arctinurus boltoni | Lichidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Cephalon, thorax, pygidium | ‘U’-shaped indentation, cephalon; ‘V’-shaped indentation thoracic segments 3–4; ‘W’-shaped indentation thoracic segments 8–10 ‘U’-shaped indentation pygidium | Left (cephlaon, thorax) Right (pygidium) | Whiteley, Kloc & Brett (2002 fig. 2.9B); Chinnici & Smith (2015, fig. 434) |
| Arctinurus boltoni | Lichidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Thorax, pygidium | Thoracic spines 1–4 truncated, ‘U’-shaped indentation, truncated pygidial spines | Right (thorax) Left (pygidium) | Chinnici & Smith (2015, fig. 432) |
| Arctinurus boltoni | Lichidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Cephalon, thorax | ‘U’-shaped indentation, posterior cephalon, single segment injury, 4th thoracic segment | Right | Chinnici & Smith (2015, fig. 433) |
| Arctinurus boltoni | Lichidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Pygidium | Abnormal pygidial spine | Left | Bicknell, Paterson & Hopkins (2019, fig. 3A, B) |
| Arctinurus boltoni | Lichidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Pygidium | Reduced pygidial spine | Right | Bicknell, Paterson & Hopkins (2019, fig. 3C, D) |
| Arctinurus boltoni | Lichidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Pygidium | ‘U’-shaped indentation | Right | Bicknell, Paterson & Hopkins (2019, fig. 3E, F) |
| Arctinurus boltoni | Lichidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Pygidium | Rounded pygidial spine | Right | Bicknell, Paterson & Hopkins (2019, fig. 4A, B) |
| Arctinurus boltoni | Lichidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Pygidium | ‘W’-shaped indentation | Right | Bicknell, Paterson & Hopkins (2019, fig. 4C, D) |
| Arctinurus boltoni | Lichidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Pygidium | ‘W’-shaped indentation | Right | Bicknell, Paterson & Hopkins (2019, fig. 4E, F) |
| Arctinurus boltoni | Lichidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Thorax | Single segment injury, thoracic segment 2 | Right | Bicknell, Paterson & Hopkins (2019, fig. 5A, B) |
| Arctinurus boltoni | Lichidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Thorax and pygidium | Two ‘V’-shaped indentations (thoracic segments 1–2; thoracic segments 7–8); pygidium slightly truncated | Right | Bicknell, Paterson & Hopkins (2019, fig. 6A, B) |
| Calymene niagarensis (Hall, 1843) | Calymenidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Thorax | ‘L’-shaped indentation, thoracic segments 1–4 | Right | Chinnici & Smith (2015, fig. 432) |
| Calymene sp. | Calymenidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Cephalon | Borings on genal spine | Left | Whiteley, Kloc & Brett (2002, fig. 2.15D–F) |
| Coronocephalus urbis Strusz, 1980 | Encrinuridae | Wenlock | Sheinwoodian | Walker Volcanics, Australian Central Territory, Australia | Pygidium | Bifurcated rib | Right | Strusz (1980, pl. 1, fig. 17) |
| Dalmanites limulurus (Green, 1832) | Dalmanitidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Thorax | ‘U’-shaped indentation, thoracic segments 2–5 | Right | Chinnici & Smith (2015, fig. 437) |
| Dalmanites limulurus | Dalmanitidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Thorax | U’-shaped indentation, thoracic segments 1–3 | Right | Chinnici & Smith (2015, fig. 438) |
| Dalmanites limulurus | Dalmanitidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Thorax | ‘U’-shaped indentations, thoracic segments 2–4 and 8–1 | Left | Chinnici & Smith (2015, fig. 439); Whiteley, Kloc & Brett (2002, fig. 2.15A) |
| Dalmanites limulurus | Dalmanitidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Thorax, pygidium | U’-shaped indentation, thoracic segments 10–11 extending into pygidium | Left | Chinnici & Smith (2015, fig. 440) |
| Dalmanites limulurus | Dalmanitidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Thorax | U’-shaped indentation, thoracic segments 5–11 | Left | Chinnici & Smith (2015, fig. 441) |
| Dalmanites limulurus | Dalmanitidae | Wenlock | Sheinwoodian | Rochester Formation, New York, USA | Pygidium | Terminal, medial spine missing | Midline | Whiteley, Kloc & Brett (2002, fig. 2.15C) |
| Japonoscutellum sp. | Encrinuridae | Wenlock | Sheinwoodian | Yarralumla Formation, New South Wales, Australia | Pygidium | Bifurcating axial rib | Right | Bicknell & Smith (2021, fig. 3b, c) |
| Exallaspis bufo (Ramsköld, 1984) | Odontopleuridae | Wenlock | Homerian | Mulde Beds, Sweden | Cranidium | Asymmetrical crandium | Left | Ramskold (1984, pl. 31, fig. 1) |
| Exallaspis bufo | Odontopleuridae | Wenlock | Homerian | Mulde Beds, Sweden | Pygidium | Additional terminal spine | Midline | Ramskold (1984, pl. 31, fig. 5) |
| Interproetus truncus Šnajdr, 1980 | Proetidae | Wenlock | Homerian | Liten Formation, Czech Republic | Thorax | Reduced and fused pleurae | Right | Šnajdr (1980, pl. XLVIII, figs 1, 2) |
| Ktenoura retrospinosa Lane, 1971 | Cheiruridae | Wenlock | Homerian | Much Wenlock Limestone Formation, England | Pygidium | Reduced spine | Right | Lane (1971, pl. 6, fig. 9a, b) |
| Odontopleura ovata Emmrich, 1839 | Odontopleuridae | Wenlock | Homerian | Liten Formation, Czech Republic | Thorax | ‘U’-shaped indentation, thoracic segments 4–8 | Right | Šnajdr (1979, pl. 1) |
| Exallaspis mutica (Emmrich, 1844) | Odontopleuridae | Wenlock–Ludlow | — | Grünlich-Graues Graptolithengestein, Germany | Pygidium | Single spine injury | Left | Šnajdr (1969, pl. IV, fig. 7) |
| Odontopleura ovata | Odontopleuridae | Wenlock–Ludlow | — | Grünlich-Graues Graptolithengestein, Germany | Pygidium | Asymmetric medial lobe | Left | Schrank (1969, pl II, fig. 4) |
| Alcymene lindstroemi Ramsköld et al., 1994 | Calymenidae | Ludlow | Gorstian | Hemse Marl, Sweden | Cephalon | Overdeveloped glabellar region | Midline | Ramskold (1994, fig. 5, 9) |
| Bohemoharpes ungula viator Přibyl & Vaněk, 1986 | Harpetidae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Cephalon | Asymmetrical cranidial region | Right larger than left | Přibyl & Vaněk (1986, pl. 2, fig.1) |
| Bohemoharpes ungula | Harpetidae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Cephalon | Multiple neoplasms | Left | Šnajdr (1978a, pl. I, figs. 1–5) |
| Bohemoharpes ungula | Harpetidae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Cephalon | Neoplasms on genal spine | Left | Šnajdr (1978a, pl. I, figs. 6, 7); Šnajdr (1990, p. 63) |
| Prionopeltis archiaci (Barrande, 1846) | Proetidae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Single spine injury | Right | Šnajdr (1981a, pl. I, fig. 1) |
| Prionopeltis archiaci | Proetidae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | ‘U’-shaped indentation | Right | Šnajdr (1981a, pl. II, fig. 2) |
| Prionopeltis archiaci | Proetidae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Fused pygidial ribs, ‘W’-shaped indentation | Right | Šnajdr (1981a, pl V, fig. 4) |
| Prionopeltis archiaci | Proetidae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Pinched pygidial ribs | Left | Šnajdr (1981a, pl V, fig. 5; pl VIII, fig. 3) |
| Prionopeltis archiaci | Proetidae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Additional terminal spine | Midline | Šnajdr (1981a, pl VII, fig. 6) |
| Prionopeltis archiaci | Proetidae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Thin terminal spines | Midline | Šnajdr (1981a, pl VIII, fig. 4) |
| Prionopeltis archiaci | Proetidae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Ribs poorly developed | Right | Šnajdr (1981a, pl VIII, fig. 5) |
| Prionopeltis archiaci | Proetidae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Additional spine | midline | Šnajdr (1981a, pl VIII, fig. 6) |
| Prionopeltis archiaci | Proetidae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Additional spine | Left | Šnajdr (1981a, pl VIII, fig. 7) |
| Prionopeltis archiaci | Proetidae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Additional spine | Midline | Šnajdr (1981a, pl VIII, fig. 8) |
| Prionopeltis dracula Šnajdr, 1980 | Proetidae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Additional spines | Both | Šnajdr (1980, not figured) |
| Scharyia micropyga (Hawle & Corda, 1847) | Aulacopleuridae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | ‘U’-shaped indentation, spine abnormally developed | Right | Šnajdr (1981a, pl IV, fig. 2) |
| Scharyia micropyga | Aulacopleuridae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Additional ribs | Midline | Šnajdr (1981b, pl. XI, fig. 1) |
| Scharyia micropyga | Aulacopleuridae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Abnormally developed interring furrows | Midline | Šnajdr (1981b, pl. XI, fig. 2) |
| Scharyia micropyga | Aulacopleuridae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Abnormally developed interring furrows | Midline | Šnajdr (1981b, pl. XI, fig. 3) |
| Scharyia micropyga | Aulacopleuridae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Abnormal axial ring | Midline | Šnajdr (1981b, pl. XI, fig. 4) |
| Scharyia micropyga | Aulacopleuridae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Abnormal axial ring | Midline | Šnajdr (1981b, pl. XI, fig. 7) |
| Scharyia micropyga | Aulacopleuridae | Ludlow | Gorstian | Kopanina Formation, Czech Republic | Pygidium | Poorly developed axial rings | Midline | Šnajdr (1981b, pl. XI, fig. 8) |
| Sphaerexochus latifrons Angelin, 1854 | Cheiruridae | Ludlow | Gorstian | Hemse Marl, Sweden | Cephalon | Pathological development on free cheek | Right | Ramsköld (1983, pl. 19, fig. 6) |
| Kosovopeltis nebula Campbell, 1967 | Scutelluidae | Ludlow | Gorstian–early Ludfordian | Henryhouse Formation, Oklahoma, USA | Thorax | Overdeveloped pleurae | Right | Campbell (1967, pl. 2 figs 5, 6) |
| Batocara robustus (Mitchell, 1924) | Encrinuridae | Ludlow | Ludfordian | Black Bog Shale, New SouthWales | Thorax | Bifurcated pleural rib | Right | Strusz (1980, pl. 3, fig. 7) |
| Batocara robustus | Encrinuridae | Ludlow | Ludfordian | Black Bog Shale, New South Wales, Australia | Pygidium | Offset axial nodes | Midline | Bicknell & Smith (2021, fig. 2a, b) |
| Batocara robustus | Encrinuridae | Ludlow | Ludfordian | Black Bog Shale, New South Wales, Australia | Pygidium | Bifurcating axial rib | Left | Bicknell & Smith (2021, fig. 2c, f |
| Batocara robustus | Encrinuridae | Ludlow | Ludfordian | Black Bog Shale, New South Wales, Australia | Pygidium | Additional axial node | Midline | Bicknell & Smith (2021, fig. 2d, e) |
| Didrepanon squarrosum | Cheiruridae | Ludlow | Ludfordian | Kopanina Formation, Czech Republic | Crandium | Asymmetric glabellar furrows | Left | Přibyl & Vaněk (1973, pl. I, fig. 1) |
| Leonaspis rattei (Etheridge & Mitchell, 1869) | Odontopleuridae | Ludlow | Ludfordian | Black Bog Shale, New South Wales, Australia | Thorax | Asymmetrical thoracic pleural spine base | Both | Bicknell & Smith (2021, fig. 3a) |
| Harpidella (Rhinotarion)setosumWhittington & Campbell, 1967 | Aulacopleuridae | Ludlow | ?Ludfordian | Hardwood Mountain Formation, Maine, USA | Cephalon | Asymmetrical cranidium | Left larger than right | Whittington & Campbell (1967, pl. 5, fig. 5, 6) |
| Prionopeltis striata Barrande, 1846 | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | Single spine injury | Left | Šnajdr (1981a, pl. I, fig. 2) |
| Prionopeltis striata | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | ‘W’-shaped indentation | Left | Šnajdr Šnajdr (1981a), pl. I, fig. 3) |
| Prionopeltis striata | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | Spines removed | Left | Šnajdr (1981a, pl. II, fig. 3) |
| Prionopeltis striata | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | ‘V’-shaped indentation | Right | Šnajdr (1981a, pl. II, fig. 5) |
| Prionopeltis striata | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | Fused, deformed ribs | Left | Šnajdr (1981a, pl. III, fig. 1) |
| Prionopeltis striata | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | ‘V’-shaped indentation | Left | Šnajdr (1981a, pl. III, fig. 8) |
| Prionopeltis striata | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Cephalon | Shallow ‘U’-shaped indentation in free cheek | Right | Šnajdr (1981a, pl. IV, fig. 5) |
| Prionopeltis striata | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | Pathological growth | Midline | Šnajdr (1981a, pl. IV, fig. 6); De Baets et al. (2021, fig. 6.2f) |
| Prionopeltis striata | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | Additional spine, posteriormost section | Midline | Šnajdr (1981a, pl. VII, fig. 2) |
| Prionopeltis striata | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | ‘U’-shaped indentation | Midline | Šnajdr (1981a, pl. VII, fig. 4) |
| Prionopeltis striata | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | ‘U’-shaped indentation | Midline | Šnajdr (1981a, pl. VII, fig. 5) |
| Prionopeltis striata | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | ‘U’-shaped indentation | Midline | Šnajdr (1981a, pl. VIII, fig. 1) |
| Prionopeltis striata | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | ‘W’-shaped indentation | Left | Šnajdr (1981a, pl. VIII, fig. 2) |
| Scharyia nympha Chlupáč, 1971 | Aulacopleuridae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | Additional ribs, asymmetrically developed | Midline | Šnajdr (1981b, pl. XII, fig. 7) |
| Tetinia minuta (Přibyl & Vaněk, 1962) | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | Reduced ribs | Right | Šnajdr (1981a, pl. II, fig. 7) |
| Tetinia minuta | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | ‘U’-shaped indentation, pinched ribs | Right | Šnajdr (1981a, pl. II, fig. 8) |
| Tetinia minuta | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | U’-shaped indentation, abnormal ribs | Left | Šnajdr (1981a, pl. III, fig. 4) |
| Tetinia minuta | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | Asymmetrical pygidium, abnormal ribs | Left | Šnajdr (1981a, pl. III, fig. 5) |
| Tetinia minuta | Proetidae | Pridoli | — | Přídolí Formation, Czech Republic | Pygidium | Asymmetrical medial lobe, abnormal ribs | Left | Šnajdr (1981a, pl. III, fig. 6) |