Home Page

Next Page

PLACODERMI Antiarchs, Ptyctodonts, Rhenanids and Petalichthyids


Bothriolepis sp. from 'Dura Den - A monograph of the Yellow sandstone' 1859 J Anderson

Characterised by having the pectoral fins modified into jointed appendages covered with dermal plates and much larger thoracic armour (comprised of 2 Median Dorsal plates) compared to the head armour (which features a single opening for the eyes, olfactory and pineal organs). The Superognathal of the antiarchs is replaced by a suborbital cutting plate. The body and tail can be covered with large scales as in Pterichtyodes or almost naked as in Bothriolepis. The diversity of this group is not great but they were probably the most common fishes of the Late Devonian although mostly limited to freshwater or deltaic environments (although Bothriolepis is also present in the Gogo fauna of the reef complexes in Western Australia which are unquestionably marine).  Strange structures associated with the pharynx have been interpreted as lungs, although this is not universally accepted.


Antiarchs in my collection (click on thumbnails to see larger images)


Pterichthyodes milleri     Mid Devonian 

Confined to the Achanarras Horizon of the MORS this fish reached acout 18cm in length.

y-ptertail.jpg (47704 bytes)  y-ptertailtail.jpg (54312 bytes)      Orkney, Scotland (note superb tail and lateral presentation)

pt17.jpg (103566 bytes)   y-plac.jpg (27008 bytes)      Achanarras, Scotland

lethenpternotail.jpg (141844 bytes)   lethenpter.jpg (146668 bytes)        Lethen-Bar, Scotland

Orig. labels sig. R.F.Damon 


Microbranchius dicki  Mid Devonian  Eday Beds, Orkney Islands

This tiny antiarch reached only 3 cm in length and was restricted to the John O' Groats sandstones and equivalents

ss-microbranch.jpg (116996 bytes)     tt-immicro.jpg (47009 bytes)


Bothriolepis canadenesis  Upper Devonian, Escuminac Formation,  Miguasha, Quebec, Canada

ss-bothriobest.jpg (80978 bytes)     bothbig.jpg (80606 bytes)  

Bothriolepis canadenesis mass mortality plate with Scaumenacia and plant material

vv-mig.jpg (62135 bytes)     vv-mig2.jpg (147040 bytes)   vv-mig3.jpg (85965 bytes)    vv-mig4.jpg (83207 bytes)




yun2.jpg (59374 bytes)    yun3.jpg (53085 bytes)    yun1.jpg (60891 bytes)


Pterichthyodes images from Woodward 1899 and  'The fishes of the ORS of Britain' Traquair, 1904

 tt-impteri.jpg (90394 bytes) tt-impterich3.jpg (75116 bytes)  tt-pter5.jpg (93805 bytes) tt-impterich4.jpg (97365 bytes)  tt-impterich2.jpg (41271 bytes)


Ptyctodont Placoderms

In many respects the Ptyctodonts (‘beak tooth’) resemble the extant chimaerids with crushing (trabecular) plates in the jaws. They are the only Placoderms that show sexual dimorphism with the male having claspers in both Ctenurella and Rhamphodopsis. They had reduced head plates, reduced thoracic shields and long bodies.

gg-cten.jpg (55875 bytes)    Ctenurella gladbachensis      U Devonian,   Bergisch Gladbach, Germany

gg-cten2.jpg (73120 bytes)   Ctenurella

jj-rham.jpg (224776 bytes)  Rhamphodopsis threiplandi,  Edderton, Scotland

Rhenanid Placoderms

These placoderms are very similar to extant skates and rays, being characterised by considerably enlarged pectoral fins (even the braincase, labyrinth and other internal features are suggestive of batomorphs) however, they are clearly placoderms as shown by the pattern of dermal plates.

ss-Gemundina.jpg (124880 bytes)    Gemuendina      Early Devonian         Bundenbach, Germany


 RHENventral2.jpg (198560 bytes)     RHENventral.jpg (303130 bytes)   RHENdenticle.jpg (164252 bytes) Jagorina.  Rhenanid. Devonian of Morocco


Petalichthyid Placoderms

Characterised by having dorsal orbits, these placoderms have widely splayed pectoral fins and long spinal plates. Lunaspis from Early Devonian Bundenbach slate of Germany is the best known example.


Acanthothoraci, Stensioellida and Pseudopetalichthyida Placoderms.