PIKAIA GRACILIENS: MIDDLE CAMBRIAN GRACE

Pikaia graciliens is an extinct, primative chordate animals from the Middle Cambrian Burgess Shale Lagerstätte of British Columbia, Canada. 

These lovelies swam by moving their bodies in a series of zigzag curves similar to the movement of eels, all the while filtering particles from the water.

Although primitive, Pikaia shows the essential prerequisites for vertebrates. When alive, Pikaia was a compressed, leaf-shaped animal with an expanded tail fin; the flattened body is divided into pairs of segmented muscle blocks, seen as faint vertical lines. 

The muscles lie on either side of a flexible structure resembling a rod that runs from the tip of the head to the tip of the tail. It swam by throwing its body into a series of S-shaped undulating movements that mimicked the movement of eels. Fish inherited this same swimming movement, but they generally have stiffer backbones so it does not quite have the same visual effect. 

Pikaia was likely a slow swimmer since it lacked the fast-twitch fibres that we associate with rapid swimming in modern chordates. Still, even that form of movement in the Middle Cambrian is impressive in terms of mobility and design.

Conway Morris and Caron (2012) published an exhaustive description based on more than one hundred known fossil specimens. Through their deeper look at this primitive marine mystery, they discovered new and unexpected characteristics that they recognized as primitive features of the first chordate animals. On the basis of these findings, they constructed a new scenario for chordate evolution. 

Subsequently, Mallatt and Holland reconsidered Conway Morris and Caron's description and concluded that many of the newly recognized characters are unique, already-divergent specializations that would not be helpful for establishing Pikaia as a basal chordate.

PTEROSAURS: SOARING ANCIENT SKIES

If you could travel through time and go back to observe our ancient skies, you would see massive pterosaurs — huge, winged flying reptiles of the extinct order Pterosauria — cruising along with you. 

They soared our skies during most of the Mesozoic — from the late Triassic to the end of the Cretaceous (228 to 66 million years ago). 

By the end of the Cretaceous, they had grown to giants and one of their brethren, Quetzalcoatlus, a member of the family Azhdarchidae, boasts being the largest known flying animal that ever lived. 

They were the earliest vertebrates known to have evolved powered flight. Their wings were formed by a membrane of skin, muscle, and other tissues stretching from the ankles to a dramatically lengthened fourth finger.

PISTA DE BAILE JURÁSICA

This busy slate grey dinosaur trackway from the Iberian Peninsula looks more like a dance floor than the thoroughfare it is. 

The numerous theropod dinosaur tracks — with a few enormous sauropod tracks thrown in for good measure — cover the entire surface. 

The local soil has a bit of rusty iron ore in it that highlights each print nicely when the soil is blown into the depressions the tracks left. 

The dinosaurs crossed this muddy area en masse sometime back in the Jurassic.

The Iberian Peninsula is the westernmost of the three major southern European peninsulas — the Iberian, Italian, and Balkan. It is bordered on the southeast and east by the Mediterranean Sea, and on the north, west, and southwest by the Atlantic Ocean. The Pyrenees mountains are situated along the northeast edge of the peninsula, where it adjoins the rest of Europe. Its southern tip is very close to the northwest coast of Africa, separated from it by the Strait of Gibraltar and the Mediterranean Sea.

The Iberian Peninsula contains rocks of every geological period from the Ediacaran to the recent, and almost every kind of rock is represented. To date, there are 127 localities of theropod fossil finds ranging from the Callovian-Oxfordian — Middle-Upper Jurassic — to the Maastrichtian (Upper Cretaceous), with most of the localities concentrated in the Kimmeridgian-Tithonian interval and the Barremian and Campanian stages. The stratigraphic distribution is interesting and suggests the existence of ecological and/or taphonomic biases and palaeogeographical events that warrant additional time and attention.

As well as theropods, we also find their plant-eating brethren. This was the part of the world where the last of the hadrosaurs, the duck-billed dinosaurs, lived then disappeared in the Latest Cretaceous K/T extinction event 65.5 million years ago.

The core of the Iberian Peninsula is made up of a Hercynian cratonic block known as the Iberian Massif. On the northeast, this is bounded by the Pyrenean fold belt, and on the southeast, it is bounded by the Baetic System. These twofold chains are part of the Alpine belt. To the west, the peninsula is delimited by the continental boundary formed by the magma-poor opening of the Atlantic Ocean. The Hercynian Foldbelt is mostly buried by Mesozoic and Tertiary cover rocks to the east but nevertheless outcrops through the Sistema Ibérico and the Catalan Mediterranean System. The photo you see here is care of the awesome Pedro Marrecas from Lisbon, Portugal. Hola, Pista de baile jurásica!

Pereda-Suberbiola, Xabier; Canudo, José Ignacio; Company, Julio; Cruzado-Caballero, Penélope; Ruiz-Omenaca, José Ignacio. "Hadrosauroid dinosaurs from the latest Cretaceous of the Iberian Peninsula" Journal of Vertebrate Paleontology 29(3): 946-951, 12 de septiembre de 2009.

Pereda-Suberbiola, Xabier; Canudo, José Ignacio; Cruzado-Caballero, Penélope; Barco, José Luis; López-Martínez, Nieves; Oms, Oriol; Ruíz-Omenaca, José Ignacio. Comptes Rendus Palevol 8(6): 559-572 septiembre de 2009.

SNOWY TREE CRICKET: CHIRPING THERMOMETERS

About 250 million years ago, our once silent world became a cacophony of diverse animal sounds. 

One of the most lyrical of those voices to join the Earth's chorus were the true crickets. We can count them as some of the earliest musicians on the planet. 

This group evolved and contributed to the nocturnal circumambience of our planet a full 150 million years before our human ancestors would have heard them for the very first time. It is their long lineage that I am mindful of when I am out for an evening stroll and hear their pleasing serenade.

If you find yourself out in the woods and are wondering what the temperature might be, you need only slip closer to the nearest stand of deciduous trees to follow the musical sounds of the wee Snowy Tree Cricket, Oecanthus Fultoni, part of the order orthoptera.

Snowy Tree Crickets and their cousins double as thermometers and wee garden predators, dining on aphids and other wee beasties. Weather conditions, both hot and cold, alter the speed at which they rub the base of their wings together and consequently regulate their rate of chirping.

Listen closely for their tell-tale high pitch triple chirp sound in the early evening. Being in Canada, our crickets chirp in Celsius. To figure out the temperature, we simply count the number of chirps over a seven-second period and add five to learn the local temperature.

If did not happen to bring your calculator and you are still operating in old-school Fahrenheit, you can use this handy conversion — double the temperature in Celsius, add 32 you'll get the approximate temperature in Fahrenheit. And if you are not all that interested in the temperature, enjoy their pleasing serenade as you take your early evening stroll. They've been working on this number for millions of years. 

Daniel Otte from the Academy of Natural Sciences in Philadelphia did up a wonderful piece on the evolution of cricket songs. If you’re a keen bean & want to learn more, I'll attach the journal article for you. https://doi.org/10.2307/3503559. https://www.jstor.org/stable/3503559