Graham Eaton / View towards Cribyn from Pen y Fan in the Brecon Beacons National Park, Wales, September. The outcrops of Devonian age, Old Red Sandstone forms escarpments carved by glaciers during the last ice age.

Graham Eaton / View towards Cribyn from Pen y Fan in the Brecon Beacons National Park, Wales, September. The outcrops of Devonian age, Old Red Sandstone forms escarpments carved by glaciers during the last ice age.

Will Watson / Maen Llia Standing Stone composed of intraformational conglomerate from the Devonian Old Red Sandstone Succession, attributed to the Bronze Age. Brecon Beacons National Park, Powys, Wales, UK. August...

Will Watson / Erratic boulder deposited beside Llansgorse Lake during the last Ice-Age, an Intraformational conglomerate from the Old Red Sandstone Succession, Devonian Period, and drystone wall, Brecon Beacons Nat...

Will Watson / Intraformational conglomerate boulder, Old Red Sandstone Succession, Devonian Period, Llyn y Fan Fawr; glacial lake, Black Mountain, Brecon Beacons National Park, Breconshire, Wales, August 2018.

Will Watson / Landslip chasm and Devonian Old Red Sandstone shattered rocks, Cwmyoy Graig, Brecon Beacons National Park, Monmouthshire, Wales, UK, October 2018.

Will Watson / Landslip chasm and Devonian Old Red Sandstone shattered rocks, Cwmyoy Graig, Brecon Beacons National Park, Monmouthshire, Wales, UK, October 2018.

Will Watson / Snow in the Olchon Valley, a U-shaped valley with shattered rocks belonging to the Senni Formation of Devonian Old Red Sandstone. Cat's Back, Black Mountains, Herefordshire, England, UK. March, 20...

Will Watson / Snow on Black Hill / Cat's Back and the Black Mountains with exposed Old Red Sandstone from the Senni Formation, Devonian Period. Golden Valley, Herefordshire, England, UK. March, 2018.

Will Watson / Devonian sandstone with trace fossil. Tetrapod tracks created by a primitive four-limbed vertebrate circa 385 Million years ago. One of the oldest vertebrate tracks in the world. Valentia Island, Coun...

Will Watson / Boulder in heathland from the Senni Formation. Mudstone layers were deposited in freshwater lakes during the Lower Devonian. Cat's Back, Black Mountains, Herefordshire, England, UK. May.

Rhonda Klevansky / Peggy's Cove Lighthouse, on Devonian granite rocks, Nova Scotia, Canada. May 2017

Juan Carlos Munoz / Site of Tetrapod footprints from Devonian period on Valentia Island, Iveragh Peninsula, County Kerry, Republic of Ireland. September 2015.

John Cancalosi / Fossil trilobite (Kettneraspis sp) from Devonian period, Morocco.

Adrian Davies / Fossil coral (Hexagonaria sp) Devonian period, from Southern Morocco

Will Watson / Geologists viewing Quartz Conglomerate exposure, Upper Devonian, Huntsham Hill, Wye Gorge, Herefordshire, UK, April 2013.

John Cancalosi / Fossil trilobite (Kettneraspis sp.) from Devonian period, Morocco.

Juan Carlos Munoz / Fossil of the prehistoric hexacoral (Acervularia goldfussi) from the middle devonian period

Juan Carlos Munoz / Fossil of a Trilobite (Ceratarges sp) from the Devonian period, Asturias, Spain

Philippe Clement / The Rock of Falize, a Frasnian limestone anticline (convex geological fold) from the Devonian era. Durbuy, Belgium

Philippe Clement / The Rock of Falize, a Frasnian limestone anticline (convex geological fold) from the Devonian era. Durbuy, Belgium

Steven David Miller / Windjana Gorge National Park is surrounded by the towering walls of a 350-million-year-old Devonian coral reef. The limestone cliffs include small caves and numerous fossils. Western Australia Septem...

Steven David Miller / Windjana Gorge National Park is surrounded by the towering walls of a 350-million-year-old Devonian coral reef. The limestone cliffs include small caves and numerous fossils. Western Australia Septem...

Steven David Miller / Cliffs composed of 350-million year old Devonian coral reef, Windjana Gorge National Park, The Kimberley, Western Australia September 2006

Steven David Miller / 350-million year old Devonian coral reef with numerous fossils, including nautiloids, Windjana Gorge National Park, The Kimberley, Western Australia

SINCLAIR STAMMERS / Fossil of Trilobite (Andegavia cf. simplex) from the Devonian period, Eifelian, Hamar Laghdad, Morocco. Pete Lawrance collection

SINCLAIR STAMMERS / Close up of fossil of the schizochroal eye of the Trilobite (Plesiomavinella pujrarii) (Wolfart 1968) from the Devonian period, Givetian, Sleasica Formation, Tikani, La Paz, Bolivia. Pete Lawrance col...

SINCLAIR STAMMERS / Fossils of Burrowing trilobites (Homalonotus / Trimerus linares) (Salter) from the Middle Devonian period, Patacamaya, Bolivia. The cylindrical body shape plus shovel nose headshield possibly indicate...

SINCLAIR STAMMERS / Fossils of Goniatites (extinct shelled cephalopods) These specimens are Devonian and preserved in haematite, they were found weathered out on desert surface in southern Morocco.

Roger Powell / Geological patterns caused by harder sediment entering the dessication cracks in the muddy edges of Lake Orcadie during the middle Devonian period 370 million years ago, Hellberry Geo, Auckengill, Cai...

John Cancalosi / Fossilised Fish (Pterichthyodes milleri) a Placoderm from the Mid Devonian period, Caithness, Scotland

John Cancalosi / Fossil tree fern {Archaeopteris sp} from the Late Devonian period, Quebec, Canada.

John Cancalosi / Tribolite fossil from devonian period. {Leonaspis williamsi} Bromide, Oklahoma

John Cancalosi / Trilobite fossils {Xenasaphus devexus} mid- devonian Russia

Paul D Stewart / Illustration of Trilobite (Phacops latifrons) enrolled and open, from 'Organization of the Trilobites' by Hermann Burmeister, appearing in the Ray Society translation of his work published in 1846. Th...

Paul D Stewart / 1856 portrait of Hugh Miller, Scottish geologist and palaeontologist, born 1802 died 1856. Photographic frontispiece of author by J.G. Tunny in some first editions of Miller's posthumous 1857 book 'Te...

Joel Sartore / Photo Ark / Greater sage grouse (Centrocercus urophasianus) female, aged 4 years, portrait, Wilder Institute Calgary Zoo's Devonian Wildlife Conservation Center, Alberta, Canada. Captive.

Joel Sartore / Photo Ark / Greater sage grouse (Centrocercus urophasianus) female, aged 4 years, head portrait, Wilder Institute Calgary Zoo's Devonian Wildlife Conservation Center, Alberta, Canada. Captive.

Joel Sartore / Photo Ark / Greater sage grouse (Centrocercus urophasianus) female, aged 4 years, head portrait, Wilder Institute Calgary Zoo's Devonian Wildlife Conservation Center, Alberta, Canada. Captive.

Joel Sartore / Photo Ark / Greater sage grouse (Centrocercus urophasianus) male, aged 3 years, head portrait, Wilder Institute Calgary Zoo's Devonian Wildlife Conservation Center, Alberta, Canada. Captive.

Joel Sartore / Photo Ark / Greater sage grouse (Centrocercus urophasianus) male, aged 3 years, portrait, Wilder Institute Calgary Zoo's Devonian Wildlife Conservation Center, Alberta, Canada. Captive.

Joel Sartore / Photo Ark / Greater sage grouse (Centrocercus urophasianus) male, aged 3 years, head portrait, Wilder Institute Calgary Zoo's Devonian Wildlife Conservation Center, Alberta, Canada. Captive.

Joel Sartore / Photo Ark / Greater sage grouse (Centrocercus urophasianus) male, aged 3 years, head portrait, Wilder Institute Calgary Zoo's Devonian Wildlife Conservation Center, Alberta, Canada. Captive.

Graham Eaton / Fan y Big, Cribyn and Pen y Fan viewed from the south east, with storm clouds approaching. These are three glacial cwm's, corries / cirques carved into the Devonian, Old Red Sandstone escarpment,...

Joel Sartore / Photo Ark / Greater sage grouse (Centrocercus urophasianus) male looking around, Calgary Zoo?s Devonian Wildlife Conservation Center, Canada. Captive.

Joel Sartore / Photo Ark / A close up of a Greater sage grouse's (Centrocercus urophasianus) male head. The animal looks around. Calgary Zoo?s Devonian Wildlife Conservation Center, Canada. Captive.

Adrian Davies / Polished fossil (Goniatite sp.) embedded in stone from the Devonian period, approximately 400 million years old, Atlas Mountains, Morocco, Africa.

Adrian Davies / Polished fossil squid (Orthoceras sp.) embedded in stone from the Devonian period, Atlas Mountains, Morocco, Africa.

Graham Eaton / View towards Cribyn from Pen y Fan, outcrops of Devonian red sandstone. Brecon Beacons National Park, Wales, September 2018.

Graham Eaton / Rock of Devonian fluvial sandstone and conglomerate beside Llyn y Fan Fach, peaks of Picws Du and Fan Brycheiniog sandstone escarpment above. Near Llandovery, Brecon Beacons National Park, Wales, UK....

Graham Eaton / Crybin, Pen y fan and Corn Du, Devonian red sandstone escarpment. View from Fan y Big, Brecon Beacons National Park, Wales, UK. July 2019.

Graham Eaton / Cwm Oergwm corrie and glacial valley of Devonian red sandstone, view towards peaks of Fan y Big, Cribyn, Pen Y Fan and Corn Du. Brecon Beacons National Park, Wales, UK. May 2019.

Marie Lochman / Oscar Range, an exceptionally well preserved fossilized Devonian Reef, Kimberley, Western Australia.

Marie Lochman / Oscar Range, an exceptionally well preserved fossilized Devonian Reef, Kimberley, Western Australia.

John Cancalosi / Fossil Lungfish (Osteolepis panderi) from the Mid-Devonian. Caithness, Scotland

John Cancalosi / Fossil Placoderm fish (Pterichthodes milleri) from the Mid-Devonian period. Caithness, Scotland

John Cancalosi / Fossil Ammonites (Coccosteus cuspidata) from the Mid-Devonian period, Caithness, Scotland