The next state up for the Geological State Symbols Across America is:
State Mineral: Almandine Garnet 1977
State Fossil: Eubrontes giganteus Dinosaur Track 1991
State Dinosaur: Dilophosaurus 2017
State Mineral: Almandine Garnet
|Almandine garnet from the Carnegie Mellon Mineral Collection.|
Garnet is typically thought of as one specific mineral, however garnet is actually a series of very similar minerals. This mineral series varies in chemical composition, resulting in different mineral names, however the chemical composition of all of the garnets share a generalized chemical composition: X3Y2(SiO4)3, where "X" can be Ca, Mg, Fe2+, or Mn2+, and "Y" can be Al, Fe3+, Mn3+, V3+, or Cr3+. Along with the different chemical compositions, there are different colors and hardnesses associated with each one as well. Crystals of garnet typically form in 12-sided "balls", that can be easy to identify within the rocks that they are found in. The name "garnet" comes from the Latin, "granatus" meaning "like a grain" because of this ball-crystal habit. Garnet is formed from the metamorphism of shale minerals, and can be found in most foliated metamorphic rocks such as schist and gneiss. Garnets can also be found in some igneous rocks including granites and granitic pegmatites. Garnet has been used as a gemstone since ancient Egypt, however recently garnet has obtained significant usage as an abrasive. Since garnet is a rather hard mineral and has no cleavage, it typically breaks into sharp edged fragments, and therefore produces a good grit for water-jet cutting or sandblasting. Garnet is a very common mineral and even high grade gemstone quality specimens can be fairly cheap.
|The Connecticut Garnet Trail|
Almandine garnet is one of the most popular and common varieties of garnet. This is partly because it is the garnet variety that has a deep red color, the color most people think of when they think of garnets. The chemical formula for almandine is Fe3Al2(SiO4)3 and the mineral has a hardness of 7-7.5, very high on Moh's Hardness Scale. Typical almandine is opaque, however it can sometimes be found in the translucent variety, which is much more common for gemstone use. Garnets in Connecticut are typically found within different formations of schist, a metamorphic rock. These schists can be found across the entire state including rocks that range in age from Cambrian to Devonian, where most of them are thought to have metamorphosed from pelitic shales. Many of the available garnet sites are highlighted along the Connecticut Garnet Trail (as seen on the map to the right). Almandine from Connecticut has been used not only for gemstones but also as an abrasive such as for sandpaper and nail-files.
State Fossil: Eubrontes giganteus Dinosaur Track
|Eubrontes track specimen #YPM VP 003454 |
from the Peabody Museum at Yale.
Dinosaur tracks are a special type of fossil referred to as a "trace fossil". A trace fossil is evidence that an animal had once been within an area but it is not the actual remains of the animal itself. Trace fossils can encompass a wide variety of features including worm burrows, foot prints, or even fossil poop (called coprolites). In many cases, trace fossils from an animal have the potential to far outnumber the amount of body fossils from that animal, because an animal can leave behind only one skeleton but they can leave behind countless footprints. Unfortunately, it is also very difficult to link most trace fossils back to the animal or animals that made them, and often that isn't even important to most scientists because it distracts from what the trace fossils are able to tell us. Trace fossils are the evidence of animal behavior. The record of behavior that is preserved by a trace fossil can include how it moved, how it responded to different stimuli, what it ate, or even how it ate. Trace fossils can also preserve the presence of animals that don't usually get preserved as body fossils, including most types of worms and insects. When identifying a trace fossils, ichnologists (the scientists who study trace fossils) will treat them in much the same way as body fossils. They are identified with a genus, or in the trace fossil sense an "ichnogenus", and an "ichnospecies", where the full name of the trace will be unique to that type of trace fossil.
|Dinosaur State Park dinosaur trackway from 50campfires.com.|
Eubrontes giganteus is a trace fossil of a footprint (pictured above right). Based on information gleaned from the trace, scientists were able to discover that it represented a bipedal (two-legged), carnivorous dinosaur. Some of that came from the tracks themselves and their shape, but some of it came from the body fossils of the animals than we knew lived at around the same time and location as these tracks were found. Dinosaur tracks were first described by Edward Hitchcock back in the mid 1800's from the Early Jurassic strata (rocks) from the Connecticut River Valley. His descriptions are the first described dinosaur tracks ever and he is considered to be one of the founders of modern ichnology. The original example of Eubrontes was discovered in what is now the Dinosaur Footprint Reservation in Holyoke, MA, from sandstones and mudstones that indicated a shallow lake environment. When Hitchcock first identified these tracks, and several similar tracks, he had named them multiple different names, with Eubrontes being one of the first names used. However, it was not THE first name used. The first name used was Ornithichnites, but this was eventually thrown out by later workers because it was a name used to describe a generalized bird track and not the animal in which made it. Hitchcock later used Eubrontes to identify the track maker, which he believed to be a large bird due to the similarity of the track to modern day birds. Although we know today that the identification of the track maker is a very difficult, if not an impossible, question to answer, it was not always the mind-set of scientists. Modern day ichnologists will identify a trace fossil based on the shape and structure of the trace, so Eubrontes is now known to encompass all similarly shaped footprints. Due to the dating of the tracks and what scientists know of the animals that were alive during the Early Jurassic, it is usually assumed that the Eubrontes tracks were created by the dinosaur Dilophosaurus, or by a closely related species. Although first discovered and described from Massachusetts, Eubrontes extends within the Connecticut River Valley down into Connecticut with several tracks identified within Dinosaur State Park (as pictured above to the left). The identification and naming of Eubrontes represents an important step in the science of ichnology and paleontology in general.
State Dinosaur: Dilophosaurus
|By Eduard Solà - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=21099013|
Made famous by Jurassic Park, Dilophosaurus was a small theropod dinosaur from the Early Jurassic of Arizona. The movie emphasized large neck flaps, on a relatively small dinosaur, that flapped open to distract its prey, giving the predator time to spit acid it its prey's eyes and eventually devour it. None of that was based in reality. In reality, Dilophosaurus was about 20 feet long and 8 feet tall (much bigger than its movie counterpart), with no acid spitting, or neck flaps to speak of. What the movie did get right were the two frills that formed ridges down the skull. The name "Dilophosaurus" even translates as two-crested lizard, that is how prominent these ridges are. Besides the frills, another characteristic of Dilophosaurus is that the premaxilla, the bone at the end of the snout, was loosely attached to the maxilla, the main tooth bearing bone. This can be seen as a kind of cleft in the upper jaw in the reconstruction below. This means that Dilophosaurus would have likely needed to kill its prey with its hands and feet, not relying on its fairly weak jaw as much.
|Reconstruction of Dilophosaurus at the St. George |
Dinosaur Discovery Site at Johnson Farm.
Photo by Sarah Gibson, used with permission.
Dilophosaurus was originally discovered in 1940 by Jesse Williams, a Navajo trading post owner from Tuba City, Arizona. The remains were found within the Lower Jurassic Kayenta Formation and were eventually described by Sam Welles in 1954 and identified as a new species of Megalosaurus wetherilli. Welles eventually redescribed the bones based on some new specimens as a new genus in 1970, this time renaming the dinosaur Dilophosaurus wetherilli. Currently all of the known Dilophosaurus material has come from the Kayenta Formation of Arizona with some possible material from Utah. And that's it. There is some debate about who the track maker for the Eubrontes footprints (as described above) was. These footprints can be found from Connecticut to the southwestern corner of Utah at the St. George Dinosaur Discovery Site at Johnson Farm, and many other places as well. By analyzing the date of the formation which the tracks are located in, as well as the size and shape of the tracks, it makes it very likely that these tracks were made by Dilophosaurus. At least, the Utah tracks were. However, looking at the Connecticut tracks is a different matter. There is little evidence that the Eubrontes tracks in Connecticut could have been made by Dilophosaurus, especially given the large distance between the sites and the lack of widespread Dilophosaurus material. So although it is possible that the tracks could have been made by an animal related to Dilophosaurus with similar proportions, it's unlikely that Dilophosaurus was ever in the New England region of the US.
Olsen, Paul E., Joshua B. Smith, and Nicholas G. McDonald. "Type material of the type species of the classic theropod footprint genera Eubrontes, Anchisauripus, and Grallator (Early Jurassic, Hartford and Deerfield basins, Connecticut and Massachusetts, USA)." Journal of Vertebrate Paleontology 18.3 (1998): 586-601.
By Eduard Solà - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=21099013
Gay, Robert. "New specimens of Dilophosaurus wetherilli (Dinosauria: Theropoda) from the early Jurassic Kayenta Formation of northern Arizona." Mesa Southwest Museum Bulletin 8 (2001): 19-23.