Acta Geologica Polonica

Fourteen symposia on early/lower vertebrates have taken place over the last 50 years, usually at about four year

intervals. An average 60 participants have taken part at these symposia, with over one hundred occasionally. The

results of the symposia have been published in proceedings. The symposia started honoring E. A:son Stensiö and

E. Jarvik. Honors were taken up at the 11th symposium in Uppsala again. Since the 13th symposium a Stensiö

award is also given to young researchers in the field.

Material of tesseraspids (Tesseraspidiformes) is reported from the uppermost Severnaya Zemlya Formation

(Lochkovian, Lower Devonian) of the Severnaya Zemlya archipelago, in the Russian Arctic, where it is associated

with other vertebrate remains, including corvaspids, acanthodians, and large but rare specimens of

osteostracans. The tesseraspid material is not abundant, and most often preserved as a “patchwork” of bony

platelets (tesserae), except for a few partly articulated specimens. We redescribe the holotype of Tesseraspis

mosaica Karatajūtė-Talimaa, 1983, whose head carapace is preserved as a flattened tube of adjacent tesserae.

This material is compared to the already published tesseraspid taxa, i.e., T. tessellata Wills, 1935, T. toombsi

Tarlo, 1964, T. mutabilis (Brotzen, 1934), T. oervigi Tarlo, 1964 emend. Dineley and Loeffler, 1976, T. denisoni

Tarlo, 1964, and T. talimaae Tarlo, 1965. All species are based upon rare and incomplete material, as no

head carapaces associated with trunk and tail are known, and so, the intraspecific variability is also unknown.

Distinction between “species” is based on the detail of the superficial sculpture of the tesserae of the head carapaces,

which is unsatisfactory. It is concluded that only four of the nominal species can be retained. A review

of all other known tessellated pteraspidomorphs indicates that our knowledge of tessellated heterostracans is

currently insufficient to support a meaningful classification.

The Lower Devonian ‘Placoderm Sandstone’ in the Holy Cross Mountains (HCM) is filled with abundant impressions

of disarticulated vertebrate remains. The only acanthodian macroremains named to date are fin spines

of Machaeracanthus polonicus Gürich. Fin spine impressions in slabs from the Winna Formation (Emsian) at

Podłazie Hill (near Daleszyce) in the southern HCM, and also the Barcza Formation (?Lochkovian) at Barcza

Quarry, Miedziana Góra Conglomerate (?Lochkovian), Gruchawka, and Zagórze Formation (middle–upper

Emsian) at Bukowa Mountain in the northern HCM, reposited in the University of Warsaw, Polish Geological

Institute-National Research Institute, Warsaw, and Natural History Museum, London collections, have been cast

and studied in order to better document this poorly known taxon. As noted in other Machaeracanthus species,

we have found that M. polonicus has two different morphotypes of spines, which abut lengthwise to form a pair

of spines. Our investigations show that the fin spine assemblage includes Onchus overathensis as well as M.

polonicus, and probably another undetermined acanthodian. The affinities of O. overathensis are reassessed.

It is here considered to be a diplacanthiform, and reassigned to the genus Striacanthus, as S. overathensis.

Acanthodian scapulocoracoids have also been identified, as well as tightly spiralled toothwhorls which could

be from an acanthodian.

Placoid and polyodontode scales of stem chondrichthyans have been found in the early Lochkovian “Ditton

Group” of the Brown Clee Hill district, Shropshire, England and at Talgarth, south Wales. One of the forms is

assigned to a new species of Altholepis Karatajūtė-Talimaa, 1997, a genus already recognised from Lochkovian

shallow marine deposits in Celtiberia, Spain and the Northwest Territories, Canada as well as the type locality in

Podolia, Ukraine. Altholepis salopensis sp. nov. is based on small polyodontode scales with typically three to eight

high odontodes; the scale form was previously considered to belong to acanthodian “Nostolepis” robusta (Brotzen,

1934). The structure of other scales formerly assigned to “Nostolepis” robusta has led us to erect a new genus

Jolepis for this scale form, which differs from Altholepis in lacking an ordered layout of odontodes. Jolepis robusta

(Brotzen, 1934), originally (and possibly still) considered to be an acanthodian, is also known from the Baltic

countries, Russia, and northern Germany (ex erratic limestones). Scales of acanthodian Parexus recurvus Agassiz,

1845, and/or possibly from the stem chondrichthyan Seretolepis elegans Karatajūtė-Talimaa, 1968 (scales of these

two taxa are barely distinguishable), and of stem chondrichthyan Polymerolepis whitei Karatajūtė-Talimaa, 1968

are also present. Altholepis, Jolepis gen. nov., Seretolepis Karatajūtė-Talimaa, 1968 and Polymerolepis Karatajūtė-

Talimaa, 1968 are found in marine deposits elsewhere; the British occurrence of these taxa adds to the debate on

the sedimentological origins of the Lower Old Red Sandstone deposits in the Welsh Borderland. The geographic

range of several early sharks is now known to extend around the Old Red Sandstone continent and beyond.

Ischnacanthus gracilis (Egerton, 1861), the only ischnacanthiform acanthodian from the Lochkovian Lower

Old Red Sandstone of Scotland, is known from hundreds of specimens in institutional collections worldwide.

Despite this relative abundance, morphology and histology of its skeletal elements have rarely been investigated.

Surface details of spines, dental elements, and scales are often not visible in specimens because they are

usually split through the middle. We have examined a broad size range of fish, from 35 mm to 250 mm long.

Several intact (not split) specimens have been collected in recent years and acid-prepared to show fine details of

the dermal and dental elements. We have also used scanning electron microscopy of scales, jaws and dental elements,

denticles and fin spines, and serial thin sectioning of articulated specimens, to document their structure.

Some of our notable observations include: identification of ventral lateral lines, double-layered subtessellate

calcified cartilage forming the jaws, and the probable occurrence of extraoral tricuspid denticles on the jaws

of most fish. Examination of the size range, body proportions and dentition of institutional specimens gives no

support for recognising more than one species in the Midland Valley localities.

The Cleveland Shale fauna represents a unique view of the time after a major Devonian extinction event

(Frasnian–Famenian) with the recovery of arthrodires (Placodermi) best represented by this most specious

North American fauna. This time was followed by an additional event (Hangenberg Biocrisis) leading to the

extinction of arthrodires (and all other placoderms). An understanding of the diversity and interrelationships of

North American arthrodires can aid our understanding of this critical time in vertebrate evolution. A new aspinothoracid

arthrodire Hlavinichthys jacksoni gen. et sp. nov. is described from the Late Devonian of northern

Ohio, U.S.A., which adds to our knowledge of this group. It provides a point of comparison to other members

of the fauna whose interrelationships are poorly known. A phylogenetic analysis supports an assignment of

Hlavinichthys jacksoni gen. et sp. nov. among the aspinothoracid arthrodires. This work has drawn attention to

the continued need for descriptive and phylogenetic analyses of this unique fauna. Decades old species descriptions

need revision along with preparation and description of new taxa. The work on Hlavinichthys jacksoni

gen. et sp. nov. here is one step in that process.

Six enigmatic fossils from the Famennian (Devonian) Cleveland Shale in Ohio, U.S.A., are interpreted here as

arthrodiran (Placodermi) egg cases. Recognition as egg cases is confirmed based on the observation of layered

collagen fibers. The presence of a tuberculated bone fragment preserved within one case confirms a vertebrate

source. The nature of the tubercles and the unique morphology of the egg cases supports the interpretation of

an arthrodiran source. Reports of Devonian egg cases are limited to either assumed chondrichthyan producers

or a putative ‘egg sac’ with a morphology atypical for any vertebrate. The Cleveland Shale egg cases thus

represent the first record for a non-chondrichthyan producer. Among placoderms, behaviors of a pelagic life

style with obligate nesting sites, reef fishes with live birth, and estuarine and fluvial nurseries, along with eggcase

oviparity testifies to the diversity of reproductive strategies. As with modern fishes these strategies may

be ecologically driven and the derived and variable reproductive biology of extant chondrichthyans is actually

a primitive condition among gnathostomes. One consequence of the diversity of reproductive strategies (dependent

on the topology of relationships) is the independent origin of internal fertilization within placoderms,

possibly suggesting external fertilization as the primitive gnathostome reproductive mode.

The Indian Cave Sandstone (Upper Pennsylvanian, Gzhelian) from the area of Peru, Nebraska, USA, has yielded

numerous isolated chondrichthyan remains and among them teeth and dermal denticles of the Symmoriiformes

Zangerl, 1981. Two tooth-based taxa were identified: a falcatid Denaea saltsmani Ginter and Hansen, 2010,

and a new species of Stethacanthus Newberry, 1889, S. concavus sp. nov. In addition, there occur a few long,

monocuspid tooth-like denticles, similar to those observed in Cobelodus Zangerl, 1973, probably representing

the head cover or the spine-brush complex. A review of the available information on the fossil record of

Symmoriiformes has revealed that the group existed from the Late Devonian (Famennian) till the end of the

Middle Permian (Capitanian).

Campyloprion Eastman, 1902 is a chondrichthyan having an arched symphyseal tooth whorl similar to that of

Helicoprion Karpinsky, 1899, but less tightly coiled. The holotype of Campyloprion annectans Eastman, 1902,

the type species of Campyloprion, is of unknown provenance, but is presumed to be from the Pennsylvanian

of North America. Campyloprion ivanovi (Karpinsky, 1922) has been described from the Gzhelian of Russia.

A partial symphyseal tooth whorl, designated as Campyloprion cf. C. ivanovi, is reported from the Missourian

Tinajas Member of the Atrasado Formation of Socorro County, New Mexico, USA. Partial tooth whorls from

the Virgilian Finis Shale and Jacksboro Limestone Members of the Graham Formation of northern Texas, USA,

are designated as Campyloprion sp. Two partial tooth whorls from the Gzhelian of Russia that were previously

referred to C. ivanovi are designated as Campyloprion cf. C. annectans. The age of Toxoprion lecontei (Dean,

1898), from Nevada, USA, is corrected from the Carboniferous to the early Permian. An alternative interpretation

of the holotype of T. lecontei is presented, resulting in a reversal of its anterior-to-posterior orientation. The

genera Helicoprion, Campyloprion, and Shaktauites Tchuvashov, 2001 can be distinguished by their different

spiral angles.

An unusual 6–8 cm layer of prismatic cartilage and matrix containing some 8,800 teeth, coprolites, incomplete

occipital spines, and denticles of Orthacanthus platypternus (Cope, 1883) occurs in the lower Permian

(Artinskian) Craddock Bonebed in Texas, USA. It is the only species of shark present in the Clear Fork

Group except for three worn Xenacanthus Beyrich, 1848 occipital spine fragments and two teeth of ?Lissodus

(Polyacrodus) zideki (Johnson, 1981) (Hybodontoidei), both being the first occurrences in this unit. Analysis

of measurements of teeth with complete bases randomly selected from 3,050 initially available teeth failed to

reveal the presence of sexual dimorphism or the discrete presence of juveniles as expected, based on an independent

study which identified the presence of Orthacanthus juvenile occipital spines. A few highly symmetrical

small teeth are present, which had not been previously observed in the Texas lower Permian. They may be

symphyseals and restricted only to juveniles. Other unusual teeth include germinal teeth and deformed teeth,

both of which occur in the Clear Fork and underlying Wichita groups. One tooth displays an apparent example

of the equivalent of an “enamel pearl” on one of its cusps. The most unusual teeth are those that appear to have

undergone various stages of resorption. Only the lingual margin of the base is affected in which the apical button

is resorbed to varying degrees until only the labial margin with the basal tubercle and the three cusps are

all that remain. If the teeth were undergoing resorption, then the perplexing problem is why the apical button

is resorbed and not the superjacent basal tubercle. Other vertebrate remains include palaeoniscoid scales and

teeth and unidentified tetrapod bone fragments, jaw fragments, and teeth. Rare fragments of bones (scales?) bear

a “comb edge” which have not been previously observed in the Texas lower Permian.

Newly collected and restudied earlier materials on an enigmatic fish Ventalepis ketleriensis Schultze, 1980

from the upper Famennian (postera – ? Lower expansa conodont zones) of Latvia and central and northwestern

Russia support its porolepiform affinities. A new family Ventalepididae fam. nova is established for this genus

upon a peculiar combination of characters, including scale structure and dermal bones ornamentation. New

records extend the distribution of this genus and the Ventalepis vertebrate assemblage on the whole to a vast

geographical zone along the south-eastern coast of the Old Red Sandstone continent. The habitat area of the

Devonian vertebrate assemblage over such a large territory within the zoogeographical province of Baltica is

established for the first time. Palaeozoogeographical analysis suggests Laurentian affinities of the Ventalepis

assemblage demonstrating the major congruency to the Belgian and East Greenland ones. These and Russian

localities are separated by a vast ORS continent. Presence of the dipnoan Jarvikia in all three locations, as well

as an Ichthyostega-like tetrapod in the Belgian one reveals palaeozoogeographical connections, which might

reflect possible dwelling not only in the near-shore continent periphery but also in the river systems of the

continent itself.

Here we use synchrotron tomography to characterise dental vasculature in the oldest known tooth-bearing

sharks, Leonodus carlsi Mader, 1986 and Celtiberina maderi Wang, 1993. Three dimensional reconstruction

of the vascular system and microstructure of both taxa revealed a complex and dense network of canals, including

horizontal, ascending and secondary bifurcated canals, as well as histological features consistent with

an osteodont histotype. However, L. carlsi and C. maderi also exhibit significant morphological differences,

showing Leonodus a typical diplodont tooth morphology with a linguo-labially elongated base, that contrast

with Celtiberina’s teeth that show a single conical cusp curved lingually with a week developed flat base mesio-

distally extended, perhaps reflecting distant relationship. These data are compatible with a pre-Devonian

diversification of the two main tooth types traditionally recognised in Palaeozoic sharks (i.e., “cladodont” vs

“diplodont”). Finally, our data demonstrate that existing dental classification schemes based on styles of vascularisation

are over-simplified, especially when Palaeozoic taxa are considered.

Sparse fish microremains have been found in marine limestones from the Middle Devonian (Givetian) Skały

Formation (Sitka Coral-Crinoid Limestone Member and Sierżawy Member), Świętomarz–Śniadka section,

Bodzentyn Syncline, Łysogóry Region, northern Holy Cross Mountains, associated with conodonts of the

hemiansatus to ansatus zones. Thelodont scales referred here to Australolepis sp. cf. A. seddoni come from near

Śniadka village, from samples dated as hemiansatus to rhenanus/varcus zones. This increases the known range

for the genus from its original find in Western Australia. The presence of a thelodont in the late Middle Devonian

in Poland extends the known distribution of turiniids around the peri-Gondwana shorelines of Palaeotethys.

The Silurian fishes from north-western Hunan, China are characterised by the earliest known galeaspids

Dayongaspis Pan and Zeng, 1985 and Konoceraspis Pan, 1992, and the earliest known antiarch Shimenolepis

Wang J.-Q., 1991, as well as rich sinacanth fin spines. Shimenolepis from Lixian County in north-western

Hunan, which was dated as the Telychian (late Llandovery), has long been regarded as the oldest representative

of the placoderms in the world. As such, in addition to eastern Yunnan and the Lower Yangtze Region,

north-western Hunan represents another important area in South China that yields important fossil material

for the research of early vertebrates and related stratigraphy. Here we summarise the Silurian fishes known in

north-western Hunan so far, and classify them into three vertebrate assemblages (i.e., the Wentang, Maoshan,

and Yangtze assemblages). Based on the updated Silurian vertebrate and stratigraphic databases, the Silurian

fish-bearing strata in north-western Hunan can be subdivided into the Rongxi, Huixingshao, and Xiaoxi formations

in ascending chronological order, which can be correlated with the Lower Red Beds, the Upper Red Beds,

and the Ludlow Red Beds in South China, respectively. A new look at the Silurian strata in Lixian suggests that

the age of Shimenolepis is late Ludlow rather than late Llandovery as previously suggested. The research on

Silurian fishes and biostratigraphy in north-western Hunan not only provides morphological data of early vertebrates,

but also offers new palaeoichthyological evidence for the subdivision, correlation, and age assignment of

the Silurian marine red beds in South China. The establishment of a related high-precision Silurian stratigraphic

framework in north-western Hunan will help to elucidate the temporal and spatial distribution of Silurian fossil

fishes, deepen the understanding of the evolution of early vertebrates, and unravel the coevolution between

Silurian vertebrates and the palaeoenvironment.