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18-480: Blue Beach is informally named. The name relates to the bluish-black colour of the cliffs. It stretches from a small creek to Avonport Station . The tidal range in this part of Minas Basin may be as high as 16 metres (52 ft). The nearest town is Hantsport , approximately 5 kilometres (3.1 mi) to the south. The beach is accessible on foot from the end of the Blue Beach Road or from Avonport Station. There

36-494: A barn near Blue Beach has displayed fossils from it, as founded by Chris Mansky and Sonja Wood. The museum plans to expand to a larger facility. 45°05′54″N 64°12′54″W  /  45.09833°N 64.21500°W  / 45.09833; -64.21500 Avonport Station, Nova Scotia Avonport Station is a community in Kings County , Nova Scotia , Canada. It is located near Avonport . The Horton Bluff formation

54-447: A new pattern of limb formation evolved, where the development axis of the limb rotated to sprout secondary axes along the lower margin, giving rise to a variable number of very stout skeletal supports for a paddle-like foot. The condition is thought to have arisen from the loss of the fin ray -forming proteins actinodin 1 and actinodin 2 or modification of the expression of HOXD13 . It is still unknown why exactly this happens. " SHH

72-411: A pattern still found in modern amphibians . The increasing knowledge of labyrinthodonts from Romer's gap has led to the challenging of the hypothesis that pentadactyly , as displayed by most modern tetrapods, is plesiomorphic . The number of digits was once thought to have been reduced in amphibians and reptiles independently, but more recent studies suggest that a single reduction occurred, along

90-421: A result of the early evolution from a limb with a fin rather than digits. "Living tetrapods, such as the frogs, turtles, birds and mammals, are a subgroup of the tetrapod lineage. The lineage also includes finned and limbed tetrapods that are more closely related to living tetrapods than to living lungfishes." Tetrapods evolved from animals with fins such as found in lobe-finned fishes . From this condition

108-520: Is a small private museum near the parking lot before the trail to the beach. It contains numerous excellent and important examples of fossils from the beach. The tides make for dangerous conditions because visitors can find themselves trapped. Visitors should familiarize themselves with the Hantsport tide table (see external references). In addition to the tides, the cliffs are quite fragile with rocks regularly giving way. Care should be taken when approaching

126-452: Is interesting because trilobites are marine, whereas the majority of the Blue Beach location is seen as a lacustrine deposit. The trilobites found thus far are restricted to a 20 centimetres (7.9 in) thick layer. Fish fossils include Elonichthys , Rhadinichthys , Canobius , Letognathus , ?Ctenodus , Gyracanthides , Gyracanthus , Acanthodidae , and Bothriolepis . Letognathus

144-417: Is located 2.5 kilometres southeast from the community. 45°6′34″N 64°14′54″W  /  45.10944°N 64.24833°W  / 45.10944; -64.24833 This Kings County, Nova Scotia location article is a stub . You can help Misplaced Pages by expanding it . Polydactyly in early tetrapods Polydactyly in stem-tetrapods should here be understood as having more than five digits to

162-451: Is produced by the mesenchymal cells of the zone of polarizing activity (ZPA) found at the posterior margin of the limbs of all vertebrates with paired appendages, including the most primitive chondrichthyian fishes. Its expression is driven by a well-conserved limb-specific enhancer called the ZRS (zone of polarizing region activity regulatory sequence) that is located approximately 1 Mb upstream of

180-465: The Carboniferous . Crassigyrinus , from the fossil-poor Romer's gap in the early Carboniferous, is usually thought to have had five digits to each foot. The anthracosaurs , which may be stem-tetrapods or reptiliomorphs, retained the five-toe pattern still found in amniotes . Further reduction had taken place in the temnospondyls , leaving the forefoot with four toes and the hind foot with five,

198-599: The cliffs due to the potential of rockfall and earth flows. The section is exposed in rocks of the Carboniferous Maritimes Basin . The Maritimes Basin opened and filled between ca. 360 Ma and 325 Ma. The Blue Beach cliffs consist of soft shales and sandstones of the Horton Group . They erode rapidly because of the high tides in combination with winter freeze-thaw and ice shaving conditions, thus continuously creating opportunities for new discoveries. Closer to

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216-417: The coding sequence of Shh ." Devonian taxa were polydactylous. Acanthostega had eight digits on both the hindlimbs and forelimbs. Ichthyostega , which was both more derived and more specialized, had seven digits on the hindlimb, though the hand is unknown. The yet-more-derived Tulerpeton had six toes on both the hindlimbs and forelimbs. It is unclear whether polydactylous tetrapods survived to

234-616: The earliest Carboniferous have been found. Flora include Lepidodendron , Calamites , Aneimites, Diplotnema, Carpolithus, Genselina. In addition, countless spores can be found. Fauna includes tetrapods, fish, arthropods (horseshoe crabs, trilobites and ostracods) and shells. Fish material is quite common, but articulated bones are very rare. Most common are scales, small ribs and teeth. Uncommon are larger bones including fin spines, jaws, cranial material, clavicles, limb bones and pelvic bones. Arthropods include Paleolimulus woodae, an extinct horseshoe crab. Contrary to some erroneous reports in

252-433: The finger or foot, a condition that was the natural state of affairs in the earliest stegocephalians during the evolution of terrestriality . The polydactyly in these largely aquatic animals is not to be confused with polydactyly in the medical sense, i.e. it was not an anomaly in the sense it was not a congenital condition of having more than the typical number of digits for a given taxon . Rather, it appears to be

270-488: The popular press, it is not the world's oldest horseshoe crab (Order Xiphosurida), but is scientifically instead the oldest paleolimulid (Family Paleolimulidae). It is known from two examples found by visitors - including a Grade 4 student. The species name honors Sonja Wood who runs the Blue Beach Museum and has studied the fossils for many years along with her husband Chris Mansky. Trilobites are also rarely found. This

288-417: The specimens from Blue Beach are all pentadactyl (five digits) or are at least functionally pentadactyl. Six morphotypes have been identified so far. Several types of arthropod trace fossils are found including trackways of Diplichnites and Diplopodichnus (possibly millipedes), Rusophycus (possibly trilobites), Paleohelcura (scorpions), and Arborichnus . From 2000 onward, a small museum formed in

306-704: The trail and lower in the sequence is the Blue Beach Member and further along is the Hurd Creek Member. Blue Beach is the type locality for the apparent gap in the tetrapod fossil record known as Romer's gap . Sir William Logan , the first Director of the Geological Survey of Canada, found footprints from a tetrapod in 1841. It remains one of very few such outcrops in the world; the others are in Scotland. In recent decades, numerous tetrapod fossils dating from

324-908: Was originally assigned to Rhizodus in the mid 1800s and later to Strepsodus . This includes the species Rhizodus (now Letognathus ) hardingi of Dawson, named after a Dr. Harding of Windsor, Nova Scotia. Similarly, Dawson's Acrolepis is now attributed to Elonichthys and his Palaeoniscus is attributed to Canobis . Tetrapod fossils include acanthostegids , ichthyostegids , tulerpetontids , whatcheeriids , and embolomeres . Trace fossils are common. Examples include tetrapod footprints, fish fin trails, arthropod trackways, wave ripples, mud cracks, rain drops, and bromolites - including coprolites, fossilized dung. The tetrapod footprints and trackways are particularly important due to their age. They are reasonably common at Blue Beach, with over 2000 specimens known. Prints of tetrapods from this era can exhibit polydactyly , or more than five digits per limb., however

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