Publications by authors named "Robert Gaines"

Article Synopsis
  • Modern poriferans are divided into four classes based on spicule structure, but classifying fossil specimens is complicated due to their varied forms and structures.
  • Fossils from early periods, notably those from the Cambrian and Ordovician, show features—like hexactine spicules—that don't fit neatly into current classifications of modern sponges.
  • A newly identified poriferan from the Drumian Marjum Formation in Utah displays unique anatomical features, suggesting that the body plan of hexactinellids may have originated much earlier than previously thought, shedding light on the evolution of early glass sponges.
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The Emu Bay Shale (EBS) of South Australia is anomalous among Cambrian Lagerstätten because it captures anatomical information that is rare in Burgess Shale-type fossils, and because of its inferred nearshore setting, the nature of which has remained controversial. Intensive study, combining outcrop and borehole data with a compilation of >25,000 fossil specimens, reveals that the EBS biota inhabited a fan delta complex within a tectonically active basin. Preservation of soft-bodied organisms in this setting is unexpected and further underscores differences between the EBS and other Cambrian Lagerstätten.

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Pyritization of soft tissues of invertebrates is rare in the fossil record. In New York State, it occurs in black shales of the Lorraine Group (Late Ordovician), the best-known example of which is Beecher's Trilobite Bed. Exceptional preservation at the quarry where this bed is exposed allowed detailed examination of trilobite and ostracod soft-tissue anatomy.

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Knowledge of Cambrian animal anatomy is limited by preservational processes that result in compaction, size bias, and incompleteness. We documented pristine three-dimensional (3D) anatomy of trilobites fossilized through rapid ash burial from a pyroclastic flow entering a shallow marine environment. Cambrian ellipsocephaloid trilobites from Morocco are articulated and undistorted, revealing exquisite details of the appendages and digestive system.

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Article Synopsis
  • The evolution of Earth's oxygen cycles has been shaped by the production and consumption of molecular oxygen, particularly during the Neoproterozoic-Paleozoic transition, which saw a significant rise in oxygen levels due to increased burial of organic carbon.
  • New research based on lithium isotopic data from marine mudstones indicates a sharp rise in continental clay formation after 525 million years ago, likely due to global climate changes and crust composition shifts.
  • A biogeochemical model suggests that enhanced continental weathering and increased clay delivery to oceans may have improved the burial of organic carbon, contributing to higher oxygen levels in the early Paleozoic oceans.
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The Cambrian explosion, one of the most consequential biological revolutions in Earth history, occurred in two phases separated by the Sinsk event, the first major extinction of the Phanerozoic. Trilobite fossil data show that Series 2 strata in the Ross Orogen, Antarctica, and Delamerian Orogen, Australia, record nearly identical and synchronous tectono-sedimentary shifts marking the Sinsk event. These resulted from an abrupt pulse of contractional supracrustal deformation on both continents during the trilobite Zone.

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Sulfate reduction is an essential metabolism that maintains biogeochemical cycles in marine and terrestrial ecosystems. Sulfate reducers are exclusively prokaryotic, phylogenetically diverse, and may have evolved early in Earth's history. However, their origin is elusive and unequivocal fossils are lacking.

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Early annelid evolution is mostly known from 13 described species from Cambrian Burgess Shale-type Lagerstätten. We introduce a new exceptionally well-preserved polychaete, gen. et sp.

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Paleoneuranatomy is an emerging subfield of paleontological research with great potential for the study of evolution. However, the interpretation of fossilized nervous tissues is a difficult task and presently lacks a rigorous methodology. We critically review here cases of neural tissue preservation reported in Cambrian arthropods, following a set of fundamental paleontological criteria for their recognition.

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Atmospheric oxygen levels control the oxidative side of key biogeochemical cycles and place limits on the development of high-energy metabolisms. Understanding Earth's oxygenation is thus critical to developing a clearer picture of Earth's long-term evolution. However, there is currently vigorous debate about even basic aspects of the timing and pattern of the rise of oxygen.

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Burgess Shale-type fossil Lagerstätten provide the best evidence for deciphering the biotic patterns and magnitude of the Cambrian explosion. Here, we report a Lagerstätte from South China, the Qingjiang biota (~518 million years old), which is dominated by soft-bodied taxa from a distal shelf setting. The Qingjiang biota is distinguished by pristine carbonaceous preservation of labile organic features, a very high proportion of new taxa (~53%), and preliminary taxonomic diversity that suggests it could rival the Chengjiang and Burgess Shale biotas.

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Negative pressure wound therapy is an effective tool for the treatment of open wounds. Occasionally these wounds are associated with injuries or procedures that require treatment with an external fixator. This article shows how a simple, inexpensive, and commercially available product can be used to prevent loss of suction around external fixator pins within the negative pressure wound treatment area.

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Unlabelled: Dead space is defined as the residual tissue void after tissue loss. This may occur due to tissue necrosis after high-energy trauma, infection, or surgical debridement of nonviable tissue. This review provides an update on the state of the art and recent advances in the management of osseous and soft tissue defects.

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The "bone-on-bone" reconstruction for adolescent idiopathic scoliosis is reviewed in this article. Extensive use over the past 18 years has identified it's functional benefits outstanding clinical results, and very limited complications. This is an extensive update of it's application, since it's introduction, 18 years ago.

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Study Design: Technical note.

Objectives: To report and describe a new free-hand technique for pedicle screw placement in the thoracic spine especially in severe deformities. Because of distortion of anatomic landmarks scoliosis, this free-hand placement technique based on pedicle access through the decancelled transverse process is a safe procedure.

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Study Design: Retrospective case series of surgically treated patients with adult spine deformity (ASD).

Objective: To report the incidence of proximal junctional failure (PJF), characterize PJF and evaluate the outcome of revision surgery for PJF. A modified classification is also proposed.

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Burgess Shale-type fossil assemblages provide the best evidence of the 'Cambrian explosion'. Here we report the discovery of an extraordinary new soft-bodied fauna from the Burgess Shale. Despite its proximity (ca.

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The purpose of this study was to determine differences in insertional articular trauma in infrapatellar tibial portal and suprapatellar portal intramedullary tibial nail insertion techniques. A cadaveric study was performed on 10 matched pairs of fresh-frozen adult cadaver lower extremities with intact extensor mechanisms. Two study groups with 10 limbs each were created: left lower limbs were treated with a standard medial parapatellar nailing portal and right lower limbs were treated with a suprapatellar tibial nailing portal.

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The technique presented is a departure from previous attempts to standardize the treatment of sternoclavicular dislocations. It offers stability without requiring extra dissection around vital intrathoracic structures and greatly decreases the risk of migration of the implant used for fixation.

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Pubic symphysis diastasis during obstetric delivery occurs rarely. Symptoms usually respond to conservative management. A nulliparous 39-year-old delivered spontaneously with an audible pop noted.

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Since the beginning of the conflicts in Iraq and Afghanistan more than a decade ago, much has been learned with regard to combat casualty care. Although progress has been significant, knowledge gaps still exist. The seventh Extremity War Injuries symposium, held in January 2012, reviewed the current state of knowledge and defined knowledge gaps in acute care, reconstructive care, and rehabilitative care in order to provide policymakers information on the areas in which research funding would be the most beneficial.

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The patterns and severity of injury sustained by service members have continuously evolved over the past 10 years of combat in Iraq and Afghanistan. The 2010 surge of combat troops into Afghanistan, combined with a transition to counterinsurgency tactics with an emphasis on dismounted operations, resulted in increased exposure of US service members to improvised explosive devices and a new pattern of injury termed dismounted complex blast injury. This constellation of injuries typically includes multiple extremity injuries, high bilateral transfemoral amputations, amputated or mangled upper extremities, open pelvis fractures, and injury to the perineal and/or genital regions.

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Surgical fires are a serious threat to the patient and surgical team in the operating room. Burns have been reported at, and distant to, the operating site, as well as within the body. The essential point to remember is that at least 1 arm of the fire triangle-an oxidizer, fuel, and an ignition source-must be completely controlled to prevent an intraoperative fire.

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